Better yet, cats that are genetically-engineered to be born without claws.
I want a phaser pistol.
An alarm clock with a few simple controls for you to customize the alarm - basically, a primitive synthesizer with a few knobs you can turn to change the sound. Do you want it to beep or drone one? Warble in pitch or cycle rapidly like an alarm? Fade in slowly or just burst on at full volume?
An iPod with an FM radio built in. It’s the only thing stopping me from buying one.
But then it would no longer be cordless, now would it? 
A radio that gets all TV stations, not just VHF stations. That way, I can listen to the Simpsons while I’m in the car. Or when there’s a blackout.
A solar-powered cell phone. My battery always dies…right when I need it!
Remote-controled rabbit ears, for when you’re too lazy to get off the couch.
Satellite dishes that work indoors and/or don’t have to be oriented a certain way. I couldn’t have satellite TV in my old apartment because my windows weren’t east-facing.
A device that FULLY removes a vocal track from any song, not just dampens it down.
I’d buy one of these in a heartbeat.
I don’t really know why, but the other day I thought it would be awesome to have a remote control spider. Not really a spider looking one, but something that had eight legs and walked with that creepy spider gait. And I’d like it to be about the size of my hand.
I’d buy this, too.
~Tasha
Bumpers that can, y’know, bump.
And not cause damage to either car.
It’s a great idea why hasn’t someone thought of it before?
When my kids (especially my son) were babies, I’d have paid BIG BUCKS for a pacifier with a remote locator chip. One that responded to a hand clap or a whistle. This would have saved me many hours of frustration and a lot of the time and money I spent going to town to buy more binkies!
A DVD that doesn’t degrade after less than a year and start freezing, distorting, etc.
I’ve always wanted the same thing. A while ago I downloaded a Winamp plugin that was supposed to do this - I wanted to rap Eazy-E’s Eazy-Duz-It over The World At Large by Modest Mouse (it fits perfectly.) But the end result was kind of fuzzy and not very precise.
An alarm clock with very customized controls. Basically, what I want is an alarm clock that, at some point while I am asleep (so number one, I would have to be able to program when I’m asleep,) it will randomly set the time forward or back in a given range, but have it be random, say anywhere from 0-20 minutes. Then, when the alarm goes off in the morning, I won’t be sure if it actually is 8:00 AM, or maybe just 7:45, but I had better get up anyway, since I could be late if I assume it’s set ahead.
Pre-sliced tomatoes in the produce department.
Great for when you’re BB-Q’ing burgers on the grill.
EyeTV running on the iMac does this now. Aside from the iMac all you need is the little tuner, which is a USB device the size of a memory stick, and a little aerial. And the Mac’s digital TV reception is simply fantastic.
I want a light sabre.
This is more of a novelty, not a “why hasn’t anyone thought of it yet”: I want an oil lamp that burns vegetable oil. (For those unfamiliar with oil lamps, no you can’t just put vegetable oil in a lamp designed for kerosene; it won’t work.) What I want essentially is a reproduction of an Argand lamp, the early-nineteenth century lamps that were used before distilled petroleum became available. Unfortunately, searching for “Argand lamp” gives thousands of hits for expensive antique collectables that were converted to kerosene or electricity long ago; in a sense the opposite of what I’m looking for. I’d be happy with an obviously modern functional reproduction. Short of hiring a craftsman to build one by hand, this seems unobtainable.
A cell phone that can reliably make and receive calls.
A solar heater for a watering trough to use in my horse’s paddock, to keep the water from freezing in the winter. There are solar chargers for electrified livestock fencing, but I have yet to find a solar trough heater.
Can’t help with an AC adaptor but a few of us ozies have replaced a 12 volt battery with cord and cars cigarette lighter plug. I can’t believe the “endless drill” is not available commercially”