Final Fantasy VII is the only one I can think of that I beat, sold, and bought back.
Others:
Most the Tony Hawk games because I wanted all the older ones (2x-P8) on Xbox. Got the Xbox version of Black Hawk Down because they falsely advertised it as a different version when it was pretty much a clone of the PC version. Quake III Arena/Team Arena, Doom 3, and Resurrection of Evil from when I bought the complete Quake and Doom packs when they were on sale on Steam (was cheaper to buy all then to buy just the ones I didn't own).