I thought my first Playstation died one time, so I bought a replacement and then opened up the first one as I wanted to see how it all worked. I noticed a small orange belt had slipped off, so I put it back on and got it working again. Sold it for £40 in the end, and to my knowledge it's still working for the guy who currently owns it.

Other than that I've had a PS2 die on me (disk drive wouldn't open), and my first Xbox 360 got the dreaded RRoD six months after I bought it. Both were thankfully replaced under warranty.