Rii
Rear Admiral
I was looking over Bioshock PS3 earlier with an eye to picking it up if the additional content over the PC version could justify the purchase. For better or worse, it doesn't, and I won't, but that I was even considering it struck me as rather unusual, before I realised that I've "double dipped" on games several times before:
Mario 64: N64 and DS versions. Mario 64 is one of my all-time favourite games and one of the few decent titles on the DS at launch. No brainer there.
Warcraft III: Standard and Collector's Editions. Having missed out at release, I stumbled across a copy of the CE several years later. Blizzard's CEs are always top notch, when the time comes the Starcraft II CE will be mine regardless of how many people I have to kill for it.
World of Warcraft: Burning Crusade: Standard and Collector's Editions. Same story as above, except weeks in place of years. Thankfully I managed to offload the Standard Edition key to a friend.
Half-Life 2: Silver Edition and The Orange Box. Wasn't by choice, HL2 is only a middling FPS, but it was the only way to obtain Team Fortress 2 and Portal at the time. I offloaded the additional key to unimatrix7 on a whim, as by that time anyone I knew who was actually interested in the game already owned it.
Donkey Kong Country: SNES and GBA. No real story there.
Through a confusing mix-up some years ago I also have multiple copies of Goldeneye 007 and Ocarina of Time here, but I only personally bought one of each.
Mario 64: N64 and DS versions. Mario 64 is one of my all-time favourite games and one of the few decent titles on the DS at launch. No brainer there.
Warcraft III: Standard and Collector's Editions. Having missed out at release, I stumbled across a copy of the CE several years later. Blizzard's CEs are always top notch, when the time comes the Starcraft II CE will be mine regardless of how many people I have to kill for it.

World of Warcraft: Burning Crusade: Standard and Collector's Editions. Same story as above, except weeks in place of years. Thankfully I managed to offload the Standard Edition key to a friend.
Half-Life 2: Silver Edition and The Orange Box. Wasn't by choice, HL2 is only a middling FPS, but it was the only way to obtain Team Fortress 2 and Portal at the time. I offloaded the additional key to unimatrix7 on a whim, as by that time anyone I knew who was actually interested in the game already owned it.
Donkey Kong Country: SNES and GBA. No real story there.
Through a confusing mix-up some years ago I also have multiple copies of Goldeneye 007 and Ocarina of Time here, but I only personally bought one of each.