Every geek occasionally suffers from gadget envy. Even if you're such an early adopter that you're already waiting in line to get an iPad, your personal collection of gadgetry is limited by that pesky thing we call "reality." Go ahead, tell me you haven't, while watching Star Trek, thought about how handy it would be to have a transporter. And who hasn't — usually right after saying or doing something stupid, or upon seeing a long shot win a race — wished he had a time machine?

So here, then, is a list of the top ten most useful gadgets from science fiction and comic books. I've restricted myself to one gizmo per source, because I could write a whole list based only on *Star Trek *or Star Wars, for examples. And I've also tried to focus on devices that would be useful without being incredibly dangerous — hence, no lightsaber (because you know you'd slice off an important body part thirty seconds after turning it on), no time machine (because paradoxes have that whole destroying-the space-time-continuum problem Doc Brown warned us about), and no transporter (because, as awesome as the idea is, I'm with Dr. McCoy that being disassembled and reassembled sounds rife with potential for serious problems). Oh, and James Bond movies are just too easy to use as source material, so they're out as well.

10. The gesture computer interface from Minority Report - Was there any geek who saw this film who didn't feel a bit disappointed when he came home and sat down at his gesture-ignoring computer? The interface was seriously cool, and, unlike many (if not most) futuristic computer interfaces in movies, actually seemed like it might be usable.

9. Mr. Fusion from the Back to the Future movies - I know the folks who made the trilogy threw Mr. Fusion in at the end of the first film because it was funny, and then were forced to stick with it when making parts II and III. But it raises some serious questions, like: If they have a device in the future that can create a fusion reaction powerful enough to generate (at least) 1.21 gigawatts of electricity out of a few pounds of garbage, why the heck do they still use gasoline in their cars? (We know they do, because not only does the DeLorean still use gas after its "hover conversion," but we also see a Texaco station being run by robots.)

8. KITT from Knight Rider - OK, so calling this "science fiction" is a bit of a stretch, but, really, KITT rocked. Speaking from my own experience, I think most guys who watched Knight Rider wanted to be Michael Knight not so much because David Hasselhoff was that handsome or awesome, but because he got to ride in KITT. Granted, KITT's AI frequently made him annoying, but mostly he did cool James Bond-type stuff, but was even cooler than any of Bond's cars. And he was voiced by William Daniels, which is also pretty cool.

7. The sonic screwdriver from Doctor Who - Sure, it's a classic deus ex machina, which is why the writers (wisely) try not to have the Doctor use it too often. But consider that, while having a frequently-used deus ex machina in a TV show is a bad thing, it would be astonishingly useful to have one in real life. I, for one, would be perfectly willing to have a device that could get me out of pretty much any trouble in which I might find myself, no matter how dull that might be for those watching me.

__6. Iron Man's armor __- There's a part of me that, intellectually, knows that there's no feasible way to make such a suit without it being crushingly heavy. Then there's the part of me that really, really wants it to actually exist, especially the version that outflew the jets. That would completely be worth wearing a heavy metal suit, though has it ever occurred to anyone to consider how incredibly inconvenient it would be to be Iron Man and have to use the bathroom?

5. The Green Lantern Corps power ring - The whole ineffectual-against-yellow thing aside, the GLC power rings are indisputably kickass. I mean, you can even use a power ring to create another power ring, which should set off a few alarm bells for anyone with even an elementary knowledge of physics, but that ability just makes it even more awesome. And, really, there are enough loopholes to get around the yellow thing. It does lead one to wonder, though: Would a jar of mustard be an effective weapon against the GLC? Inquiring minds want to know.

4. The universal translator from Star Trek - How incredible is the Star Trek universal translator? It's so incredible that it even beats out the Babel Fish, since the latter only works one way. Of course, it's clear to anyone with half a brain that the device was only invented (essentially as a retcon) because it allowed the writers to avoid including a scene dealing with language differences in practically every episode. But consider how incredibly useful it would be, even if it would send every interpreter on Earth to the unemployment office.

3. The neuralizer from Men in Black - Who hasn't wanted to be able to modify someone else's memory, or his own? It would be very, very easy to go wild with one of these, of course, so they would have to be restricted only to people with impeccable ethics. But think how convenient it would be: "Honey, look here for a second. [FLASH] I didn't forget our anniversary. In fact, I brought you breakfast in bed, and gave you your gift first thing in the morning... and it was wrapped really well!" Of course the movies didn't address the question of what you should do if the person whose memory you want to rewrite happens to be wearing sunglasses, but that's a minor quibble.

2. R2-D2 from Star Wars (obviously) - C3PO is an irritating, bumbling fool when you get right down to it. R2-D2, on the other hand, is smart, funny, and astonishingly useful. He's got attachments galore, and can hack into any computer anywhere just by plugging into it. He's got enough room to store your lightsaber, should you need him to, and consider: if he can do partial repairs on an X-Wing in mid flight, think what he could do with your car!

1. The matter compiler from Neal Stephenson's The Diamond Age - It's essentially the same as the replicator from Star Trek, but I don't want to violate my one-item-per-source rule. (See also Charles Stross's Singularity Sky, with its cornucopia machine.) A machine such as this would have countless uses — and imagine the ads: "You thought it was quick and easy making coffee from a one-use pod! Now just say 'Coffee, Kona, hot, with half-and-half,' and there you have it!"

What didn't I list that I should have? Please leave a comment.