I did, i bought diablo 2 in release, than bought the expansion, bought the pack with the expansion+game because the disk of the expansion were scratched and the buying the pack or just the expansion would be the same price. Than i bought it again because it was very cheap. I think this why Blizzard games uses to have legs, people buy more than one copy of their games!

Well Pokemon games over and over. Like i bought Pokemon red and green. I hate how they only allow 1 save per game pak.

i have oblivion on xbox but then my xbox broke i then got oblivion GOTY edition for ps3

FF VIII
Resident Evil 2
Assassin's Creed, first for my 360 then for my PS3 a year later.

*Edit: Alundra 2, FF VII, Castlevania SotN.

Tales of Symphonia is the only one I can think of. I've gotten ones from the VC and what not but those don't really count.

only when ive gone to replay and old game and realized i must have traded it in a few years ago ,then i will go buy it on the cheap somewhere

Many, quite a few of them because I sold a game, and then I wanted to refill my collection. A few have been so I can play against my brother and then I have 2 copies of Mass Effect, just cause

Lets see:

• Left 4 Dead -- I bought the 360 and PC versions (and incredibly happy with both)
• The Orange Box -- Same as above
• Final Fantasy XI -- When I wanted to get the Wings of the Goddess expansion I had to buy one of the packs that had the full game and all the other expansions I already had.  Funny thing is that pack was cheaper than the Wings of the Goddess expansion by itself.
• Ghostbusters: the Video Game -- 360, PS3, PC, and Wii.  Probably eventually get the DS version too.
• Starcraft II -- I've probably bought that 5 times now because I keep losing the damn discs.
• Freedom Fighters -- Originally bought it for the Gamecube but I hated the controls so I bought it for the PS2 a few days later.  Both games together cost me maybe $10 and it was well worth it.
• Eternal Darkness -- Douchebag roommate took and sold my copy so bought another copy a few years later.
• Final Fantasy VI -- I've bought that game about a bajillion times (though all different versions)
• Just about all of my SNES collection save a few gems (was rebuilding it for a while).

I think that's about it.  I'm probably missing something but that's what I remember at the moment.

No, but I will probably end up with multiple copies of Metroid Prime 3 when I buy the Metroid Prime Trilogy. Not necessarily the same thing but close.

yep several times because I can't remember if I have already bought a game.

Legend of Dragoon 3 times first time I lost my copy (gave to a friend never got back) and 2nd and 3rd time I bid on 2 new copies and won both.