Sure, a truly awesome FPS was released last week (Call of Duty: Modern Warfare 2, for those of you living under a rock), but if you're too broke, too cheap, or just too plain lazy to go out and buy it, you can still get your game on with these online shooters, all of which are free to play on your PC.

A brand-new free-to-play shooter, Alliance of Valiant Arms runs on the Unreal 3 engine and is set in a modern-day scenario where war has broken out all over the world. Like most recent free-to-play games, players can choose to spend a small amount of money for better items; the game also features three different character classes (Rifle Man, Point Man and Sniper) and team-based tactical combat.Developed as a PR and recruiting tool for the U.S. military, America's Army has been letting people pretend to be soldiers since 2002. The third installment boasts training, technology and weapons that are in line with what the Army uses today. If you're looking for the most realistic war experience for free, AA3 is your best bet.If realism turns you off, the cartoony art style of Battlefield Heroes may be right up your alley. An installment of EA's Battlefield series, Heroes implements certain franchise elements, such as the class system, but they're a bit more limited than what you find in the retail games. Heroes also has a microtransaction-based system where you can pay small amounts for better items (including weapons and attire) in the game.Similar to Call of Duty and Counter-Strike in gameplay, Combat Arms offers players full customization of both their character and their weapons. The game is set in modern times and features a skill-based reward system. Players earn in-game currency by completing missions, which can then be used to buy better weapons and armor. Certain items can also be purchased via microtransactions, though it's worth noting that the only differences between weapons you can earn and purchase with real money are cosmetic.One of the truly free-to-play online shooters, Quake Live is the latest installment in what has become one of the most respected game franchises in history. Completely web-based, Quake Live can be played from any computer with an Internet connection, and updates to the game are made on a regular basis. With so many games based on the Quake engine, it makes sense to check out what's coming from the original developers.Originally a pay-to-play game, Savage 2 has now gone free-to-play, with the option of upgrading to a premium account. The game itself combines elements of RTS, RPG, and shooter to make for a slightly deeper experience than a straight shooter. The game also boasts protected servers for new players, so you don't have to worry about getting your ass kicked by a much more experienced player.Built using the Quake engine, Tremulous is a sci-fi, shooter-RTS hybrid that is completely open source. Players can choose to play as either humans or aliens, with each race having its own unique gameplay experience. Tremulous has garnered a number of rave reviews and awards, including a player's choice game of the year award from ModDB.com.Another game built using the Quake engine, Urban Terror is billed as a "Hollywood tactical shooter," with the emphasis being on fun over realism. While the game is fairly realistic and features real weapons, the gameplay can often be over-the-top. Like Tremulous, Urban Terror has received a number of accolades and great player reviews.Originally planned as an add-on for Return to Castle Wolfenstein, Enemy Territory is another of the truly free-to-play online shooters. Featuring the same type of gameplay as the previous Wolfenstein games, Enemy Territory is set during World War II and features team-based online play with five character classes from which to choose (soldier, medic, engineer, covert ops and field ops).Based on a comic strip by a German artist, World of Padman started off as a Quake III Arena mod and evolved into a game of its own. It features Quake-like gameplay but a cartoony art style. The game is another one that aims to make things easy for newcomers while still providing a deep experience for veterans.