Double Dipping and You... Guilty or Not Guilty?

No I'm not talking about when you're at a party and you dip your chip into the ranch dressing again after taking a bite.  (that's gross, don't do that mkay)

In the world of gaming:
Double Dipping: To buy another copy of a game that you already own, usually on a different platform/format.

Why would someone do this?  You already own a copy of the game so just play it again!
While most people have this logic, not all gamers see it that way.
>You buy a game on console but maybe you'd like it better with PC controls (or vice versa), so you buy it again.
>You buy one copy on Console A but some of your friends are over on Console B so you buy it again to join the game.
>You love a game so much that you just want to collect them all!
>You'd like to play the game again but you want to earn trophies/achievements on the other platform.
>You buy the game at release but many months later a GOTY edition comes out with DLC you were waiting for.
>You are an achievement/trophy whore and want to stack your games by playing them from another region code.

There are a few reasons for my double dippings, most are achievement/trophy related. >.>
Here's what I'm guilty of double dipping on:

If you see 2 from the same platform, they are from different regions and have stackable trophies or achievements.

Not listed:
PC/PS3/360 version of Borderlands (co-op buddies on all platforms... <3 this game)
PC/360 version of Mass Effect (prefer console version, bought PC first)
PC/360 version of The Orange Box (Steam sale had it for cheap, couldn't resist)
PC/360 version of Bioshock (I didn't like the PC controls)
PC/XBLA version of Plants vs Zombies (don't care for the XBLA version)
PS3/360 Mini Ninjas (forgot to throw it in the pic)
PC/360 Left 4 Dead (co-op with pals on both systems)
PC/360 Left 4 Dead 2 (ditto)

Okay people... what games have you purchased twice?  Fess up!