Power armor and exoskeletons are a staple in science fiction. They enhance the abilities of futuristic soldiers on the battlefield, giving them an edge against their enemies. Recently, my colleague Lauren Goode finished out the second season of her series Next Level by checking out the promising future of exoskeletons in the workplace. She mentioned that while these devices have their roots in military technology, designers are hoping that they can be used to help help workers on the job or prevent them from getting injured, or assist the disabled move around.

Given those military roots, however, it shouldn’t come as any surprise that science fiction authors, game developers, or movie directors will use some sort of exoskeleton or suit of powered armor for a pivotal battle sequence — starting with Robert Heinlein’s classic novel Starship Troopers all the way up to games like Halo or films like Iron Man.

But not every set of power armor is equal, and there are some that might be better to come up against than others. Here’s 18 examples, ranked from what you wouldn’t want to run into in a fight to what you really don’t want to run into on the battlefield.

Caterpillar P-5000 Work Loader, Aliens

The Caterpillar P-5000 Work Loader from James Cameron’s Aliens is an iconic piece of sci-fi hardware, and we’ll probably see something similar in the real world before too much longer. It’s designed to allow workers to quickly and easily move heavy pieces of equipment and cargo around.

But while Ripley demonstrated that it can be a formidable weapon in the right hands, it’s not really designed for fighting. It’s a glorified fork lift, and it’s pretty slow and cumbersome. But it’ll do in a pinch.

Exo-Suit, Elysium

In his 2013 film Elysium, Neill Blomkamp populates his world with plenty of combat robots, but humans have their own augments as well. When Matt Damon’s character Max tells a crime boss that he’s willing to storm the film’s titular space station, he’s outfitted with an exoskeleton that’s grafted to his arms and legs, while the film’s villain, Kruger has a more advanced version of his own.

The Exo Suit from the film has its roots in real-world technology, and while these might have been designed for work, the film’s characters use them to give them an edge in a fight. There are some drawbacks, though. These suits don’t provide much armor, giving an opponent plenty of weak points to strike, and they’re drilled right onto a subject’s bones, meaning that you can’t easily take them off.

Exo Suits, Call of Duty: Advanced Warfare

Set in a near future where private military corporations wage war on behalf of the governments of the world, 2014’s Call of Duty: Advanced Warfare prominently features exoskeletons that enhance a player’s movements in the game.

The game’s characters are equipped with Exo Suits, a frame that allows them to jump incredible heights, punch through doors, and more, which gives them incredible power and freedom of movement on the battlefield. The suits help speed up the game, and allow for plenty of add-ons to go into battle with.

Combat Jackets, Edge of Tomorrow

Doug Liman’s 2014 film Edge of Tomorrow features humanity fighting off an alien invasion, using heavy-duty exoskeletons called Combat Jackets to help soldiers on the ground run faster and carry heavy weapons into battle.

These combat jackets provide both extra strength, some armor, and heavy weapons for the soldiers that wear them. But they’re just a bit shy of being proper power armor, and it feels like they could stand to get some better head protection.

LCS Exoskeleton, Linda Nagata’s The Red trilogy

In her military science fiction trilogy The Red (The Red: First Light, The Trials, and Going Dark), Linda Nagata introduces readers to a group of specialized soldiers under the command of Lieutenant James Shelley: a linked combat squad. These soldiers head into the field with an impressive kit: an exoskeleton that lets them carry heavy loads and weapons into combat. But it also connects to neural laces implanted in their heads and links them to one another, making the entire unit a formidable adversary. They also have the incredibly creepy side effect of being able to walk their dead wearers back to base on their own after a battle.

The suits aren’t fully armored, but they provide quite a bit of protection to their wearers, and can be used in a variety of environments, from the African plains to high above the Arctic Circle.

Amplified Mobility Platform, Avatar

While James Cameron introduced the power loader to audiences in Aliens, he featured their militaristic cousins in his 2009 film Avatar. The Amplified Mobility Platform (also known as an AMP suit) is used by the RDA Corporation on Pandora for everything from moving around cargo to combat.

These massive suits are equipped with massive autocannon and a large knife, which gives its driver plenty of firepower. But while they’re agile in the field, their size makes them a bit of an easy target: the native Na’vi of Pandora were able to take them down with a variety of low-tech tactics.

Delta-6 Accelerator suit, G.I. Joe: The Rise of Cobra

Set in the near future, 2009’s G.I. Joe: The Rise of Cobra, shows a world that’s come under threat from a mysterious group called M.A.R.S., led by James McCullen (Christopher Eccelston). The G.I. Joe team is called out to help deal with the threat, and along the way, are provided with a couple of Delta-6 Accelerator suits.

These suits provide some armor to their wearers and provide them with an array of weapons, but have an emphasis on speed: Duke and Ripcord use them to zip around Paris. However, while they’re fast, they don’t appear to have been created in large numbers.

T-51b / T-60 power armor, Fallout

This set of armor was the standard issue for soldiers in the United States Army's Mechanized Cavalry Regiments before the Great War in the Fallout franchise. These suits carry with them a small fusion reactor for power, and can deflect laser blasts and conventional rounds.

However, in Fallout’s post-apocalyptic world, these advanced suits were harder to come by or maintain, and they’re largely used by the Brotherhood of Steel or the Enclave. They’re also not invulnerable: they’ll degrade during a heated fight.

Scout Suit, John Steakley’s Armor

While the power armor in novels such as The Forever War and Starship Troopers are well known to science fiction fans, an underrated read is John Steakley’s 1984 novel Armor. In it, a soldier named Felix deals with the psychological stresses of interstellar warfare, equipped with a suit of armor called a Scout Suit, made up of a nearly indestructible material known as plassteel.

“Two meters tall, they weighed six times the norm. Their armored powered hands could crush steel, stone, bone. Armored legs could propel the fasted around 100 kilometers per standard hour. The suit protected them as well, automatically and instantly distributing most concussions in an evenly expanding patter from the point of impact to the entire surface of the armor. “

They’re also equipped with enough life support for three days, as well as a complement of guns and bombs. While these suits are nearly indestructible, Felix comes to fear the raw power at his disposal.

Crynet Nanosuit, Crysis

The Nanosuits used in the Crysis series equip soldiers on the battlefield with an enormous amount of power, thanks to the use of artificial CryFibril muscle fibers. These suits give their wearers incredible protection, strength and speed, as well as some really useful features, such as active camouflage. They can also enhance a wearer’s vision, and allow them to survive underwater.

The big downside to these? They bond right to their wearer, and they’re nearly impossible to remove without killing them, and if they’re at risk of falling into enemy hands, they can self-destruct.

Fighting Suit, Joe Haldeman’s The Forever War

One of the best military science fiction novels out there is Joe Haldeman’s The Forever War, which drew off of his own experiences fighting during the Vietnam War. In this book, Haldeman’s soldiers are equipped with what they call a Fighting Suit, which they describe as “the deadliest personal weapon ever built.”

These suits are powerful: they can theoretically rip a steel beam in half, and provide armor and life support for a soldier to operate in a variety of hostile environments. But trainees are warned: the suits are dangerous not only to their foes, but to themselves. If they’re not careful, mistakes can be fatal.

Goliath Mk Ⅲ Powersuit, James S.A. Corey’s The Expanse

In The Expanse, Mars possesses the most advanced military force in the solar system, and its elite Marines are trained to operate in deep space, onboard spaceships, and planetary surfaces. They come decked out in a powerful suit of armor called the Goliath Powersuit. This armor completely protects its wearer, providing life support and armor, as well as a heads up display to help soldiers with targeting. They also come equipped with guns mounted directly into their arms, and carry a small rack of missiles on their backs.

These suits will resist small arms fire, and are small enough that they can be used inside the narrow corridors of a spaceship. But they’re not invincible, as Bobbie Draper’s Marines discovered on Ganymede during the television show’s second season.

Prawn Bio-Suit, District 9

When the alien Prawns arrived on Earth in Neil Blomkamp’s 2009 film District 9, they bring with them an array of advanced weapons and technologies. One such piece of equipment is a Bio-Suit, a mechanized walker that comes loaded down with a number of guns and rockets.

After he was infected by a Prawn fluid that begins to transform him, Wikus van de Merwe gets into one of the suits while he’s on the run from a gang, and he uses it to kill his attackers. These suits can give a single soldier an edge in a firefight, but only Prawns (or people transforming into one) are the only ones who can use them. While they carry an impressive range of deadly weapons, they also aren’t invincible. As Wikus battles the MNU soldiers trying to capture him, the suit takes crippling damage from a sniper rifle, as well as rockets and a truck.

Iron Man Mark III and Variants, Iron Man

Marvel kicked off its cinematic universe with 2008’s Iron Man, in which Tony Stark, the head of defense contractor Stark Industries, is captured in Afghanistan. He escapes his captors by building a primitive armored suit, but after returning home, he refines the design and its capabilities. We see him use a huge range of suits over the course of several movies, which to serve a number of specialized purposes.

Stark’s Mark III armor is a powerful piece of equipment. Powered by an arc reactor embedded in Stark’s chest and managed by an AI, it can fly, carry incredible weight, and attack enemies with rockets, guns, hand-mounted repulsers, and a chest beam. The downside? While he has an entire house full of the suits, Stark is reluctant to lend them out to the government, and it’s safe to say that they’ll only work with him in control.

Trans-Developmental Biogenic Alloy, Karin Lowachee’s “Nomad”

In Karin Lowachee’s fantastic short story “Nomad” in John Joseph Adam’s 2012 anthology, Armored she introduces readers to an armored suit known as Radical Two (nicknamed Mad). Mad is part of a rogue band of armored soldiers, and when its human, Tommy, is killed, it decides to go nomad — striking out on its own — only to pick up an inexperienced kid.

These suits are pretty powerful, and mentally link up with their human operator. These suits of armor are sentient on their own, but they prefer to fuse with a human. They’re loaded down with weapons such as guns and grenades, and are incredibly hard to kill, with or without a human helping them.

MJOLNIR Powered Assault Armor, Halo

When humanity took to the stars in Bungie’s Halo franchise, the United Nations Space Command waged a constant war against an the Insurrectionists, and developed a super soldier program to augment their forces. The SPARTAN-II program enhanced and trained the soldiers who would wear the MJOLNIR armor, and they became a formidable force on the battlefield.

The Spartans are huge, covered in a tough armor that allows them to absorb shots from enemy soldiers, along with an energy shield that provides an additional level of protection. Their suits can also host an AI to support its wearer, and can interface with the weapons that they’re using, and despite their size, they’re incredibly agile, and present a formidable threat to the Covenant and Insurrectionists.

Mobile Infantry Powered Suits, Robert A. Heinlein’s Starship Troopers

It’s hard to beat the grandaddy of them all: the power armor at the center of Robert Heinlein’s novel Starship Troopers. Almost every instance of power armor in popular culture comes from Heinlein’s use.

Powered armor is one-half the reason we call ourselves “mobile infantry” instead of just “infantry.” Our suits give us better eyes, better ears, stronger backs (to carry heavier weapons and more ammo), better legs, more intelligence, more firepower, greater endurance, less vulnerability.

These suits can operate on a variety of planetary surfaces and environments, and come equipped not only with rifles and high explosives, but also tactical nuclear warheads that can eliminate an opponent in seconds. Let’s hope that the planned reboot of the film will include it this time.

Space Marine Power Armor, Warhammer 40K

While it’s hard to beat Heinlein’s mobile infantry, the Space Marines of Warhammer 40K will do the trick. Fighting for the Imperium of Man, they have been genetically modified, conditioned and trained to become the best soldiers on the galaxy. Standing two meters tall, they’re incredibly tough, and wear imposing armor made up of thick ceramite plates.

This suit of armor links to a wearer’s nervous system, and fully protects them from their outside environment, meaning that they can operate anywhere in the galaxy. It enhances their senses and allows them to carry incredibly powerful and heavy weapons into the field. If you see them on the battlefield, just walk away.