Not many, really. Off the top of my head:
- I have 2 DS lites whose right hinges are broken. Both still sort of work, though. One of them, additionally, developed a red tint on the top screen 2 years after being dropped in a creek and turned on immediatly after retrieving it (which, admittedly, is my fault).
- My launch PS3 freezes after reading any blu-ray disc for about 10 minutes. Everything else (PS1 and PS2 games, CD and DVD playback) works perfectly, and I can technically play PS3 games or watch a blu-ray movie in 10 minute segments, but I consider it dead (because I own a PS1, PS2 and a PS3 slim, rendering the old PS3 redundant).
- A Famicom Disk system. All it does anymore is making an ungodly noise while trying to read a disk. I guess some belt ripped, but it's effectively dead until I look into it.
- There also was a Dreamcast with a dead GD-ROM drive, but it's since been revived after replacing the drive with a new (old) one.
- And lastly, a DSi whose right shoulder button stopped working. I sent it back to amazon.de and received a full refund, which I put toward the then soon to launch 3DS.