DS Lite. Wasn't really playing my DS all that much, and then bought the DS Lite when they came out over here. Didn't really see much use to be honest, and I'm glad I got rid of it now. (though I still have a few games I wasn't able to get rid of at the time)
PSP. I've had three of them at this point I keep buying them when there's a couple of games that interest me. (bought the last one for Loco Roco and UGnG) I've tried demos for a lot of the more recent games, but there's really been nothing of interest since. I still don't think there's been much worth buying at all since it launched really: Lumines / Ridge Racers are the best games on the system. I told myself I wouldn't sell this one as I'd end up buying another, but it'll have been well over a year since I bought this one and as there's the new model, it's probably not worth much at all if I did want to get rid of it now. I pretty much only use it for browsing the web if I've not got access to my laptop, which is very rare. (e.g. reinstalling Windows on it)
Wii. No games worth getting since Mario Galaxy, nothing of interest in future, Virtual Console is all but dead now. The only reason I haven't sold it yet is because it's an import system (hassle) and because I'd basically lose whatever I've spent on VC titles.
Any special edition that didn't have a proper soundtrack. It's basically the only thing that interests me about a special edition these days, and 90% of the time it's just a sampler rather than a proper soundtrack. I nearly bought the Bioshock one with that stupid figurine for it, but fortunately I found out it was only a three-track disc rather than a soundtrack CD. Mass Effect was the last one that I remember buying, and not only did it not have the full soundtrack, it was formatted as a 360 disc so you had to play it in that!
Guitar Hero 3. I've had all three Guitar Heroes, and I've sold them all. They're fun, but I'm not into buying DLC for them, so I'm interested for a month or so and then I'm just completely bored. Another thing that's hassle to get rid of, and I'd lose money on as it's been reduced and there's a new one out soon.
Too many downloadables to mention. They generally don't keep your attention for as long as retail games (not just the length, but the replayability) and when you're done with them you're stuck with them. You can't trade them in, sell them on, give them away or loan them to a friend like you can with retail games. For this reason, I never want to see retail disappear for digital distribution. I generally only end up paying £10 or so for any new games I buy now as I usually have something fairly recent to trade in towards it.
Non-gaming:
Grado GS1000 headphones. I absolutely love the sound of them, but they've never quite fit my head right (they're big) and I don't use them much these days. Another one of those things that's probably tough to sell on, and I'd lose at least half of what I paid for them. (£1000 when they just came out
)
Every HDTV I've ever bought. They might be better than CRTs in some ways, but they're worse overall, and cost significantly more
Any of the 5.1 kits I've had. I've had really cheap stuff, mid-range gear, and I just can't help thinking it's a gimmick. I'm happy enough with a high-end stereo or headphone setup.