Only one I can remember. When I was younger, I got Suikoden II for my birthday (imagine that as a present nowadays to an RPG fan?) and played it and didn't think too much of it. A while later I sold it (or gave it away to a friend).
I was fine for, say, a few months, and then I started to desperately want to play that awesome game again. I must've matured in that small time period.
I looked on eBay and couldn't believe the prices I was seeing for used and/or new copies. I was upset...until my brother's friend brought over some of his games, one of which being Suikoden II. He said that he didn't really like it, so I asked if I could borrow it, and he let me...
...I still own his copy today. Apparently he only likes sport and racing games now anyway, so...win-win, eh..? (I don't know if this counts; it sort of ended happily.

)
Jam it back in, in the dark.