So what games have you double dipped? I guess this only applies to those who shifted from console to PC or who are also into IOS gaming.
So far:
- Hotline Miami
- SC Chaos Theory
- BLEED
- The Walking Dead
- One Finger Death Punch
- Kairo
- Dark Souls
- Vector
- Stealth Bastard
- Organ Trail
Looking at State of Decay next. Still haven't finished Bioshock so I might get that on PC too
From a cursory glance at my pile of console games (and the couple of games I recall buying on XBLA):
- Alan Wake (X360, PC)
- Alan Wake's American Nightmare (XBLA, PC)
- Assassin's Creed (PS3, PC)
- Assassin's Creed II (PS3, PC)
- Batman: Arkham Asylum* (PS3, PC)
- Bionic Commando (PS3, PC)
- BioShock (PS3, PC)
- BioShock 2 (PS3, PC)
- Braid (XBLA, PC)
- Call of Duty: World at War (PS3, PC)
- Call of Duty 4: Modern Warfare (PS3, PC)
- Dark Sector (PS3, PC)
- Dead Space (PS3, PC)
- FEAR + expansions (X360, PC)
- FEAR 2 (PS3, PC)
- Gears of War (X360, PC)
- GTA: Episodes from Liberty City (X360, PC)
- Just Cause (X360, PC)
- Mass Effect (X360, PC)
- Mirror's Edge (PS3, PC)
- Prince of Persia 2009 (PS3, PC)
- Prototype (PS3, PC)
- The Orange Box (X360, PC)
- Tomb Raider: Underworld (PS3, PC)
- Unreal Tournament 3 (PS3, PC)
- Various Lego games (PS3, PC)
* Standard on PS3, GOTY on PC.
On the PC itself, excluding indie bundles:
- Aquaria (developer's website, Steam)
- Alice: Madness Returns (retail, Steam)
On Steam itself (excluding betas/test versions, remakes and the Blood Bowl games):
- American Mensa Academy/Mensa Academy (NA version/EU version)
- Batman: Arkham City (standard version, GOTY version)
- Battle vs Chess/Check vs Mate) (E version/NA version)
- Borderlands 2 (RU version, rest-of-world version)
- Cities XL (standard version, Limited Edition)
- Company of Heroes + expansions (original versions, "New Steam Version")
- Dawn of Magic 2/Time of Shadows (EU version/NA version)
- Deus Ex: Human Revolution + The Missing Link (standard versions, Director's Cut)
- Dishonored (RU version, rest-of-world version)
- Divinity 2 (Ego Draconis, The Dragon Knight Saga, Developer's Cut)
- Doom 3 (standard version, BFG Edition)
- Dragon Age: Origins + Awakening (standard versions, Ultimate Edition)
- Duke Nukem Forever (RU version, rest-of-world version)
- Dwarfs!? (original version, F2P version [via DLC purchases])
- East India Company + expansions (original versions, Gold Edition)
- Fallout 3 (original version, GOTY Edition)
- Fallout: New Vegas (RU version, rest-of-world version)
- Final Fantasy XI: Ultimate Collection Seekers Edition (NA version, EU version)
- Football Manager 2012 (RU version, rest-of-world version)
- Football Manager 2013 (RU version, rest-of-world version)
- Governor of Poker (standard version, Premium Edition)
- King Arthur + expansion (standard versions, Collection)
- Lost Planet: Extreme Condition (standard version, Colonies Edition)
- Mafia 2 (JP version, rest-of-world version)
- Majesty: Gold Edition (original version, HD)
- Majesty 2 (original version, Collection)
- Max Payne (FR version, IT version, RU version, rest-of-world version)
- Max Payne 2 (DE version, IT version, RU version, rest-of-world version)
- Street Fighter IV (original version, SSFIV:AE)
- Take on Helicopters (RU version, rest-of-world version)
- Tom Clancy's HAWX 2 (NA version, EU version)
- Who Wants to Be a Millionaire? (NA version, EU version)
I've probably missed some stuff here and there, but that'd be most of it, I'd say.