Is there a game on your hard drive that you just can't delete? or perhaps a piece of DLC that you wont part with because of some bizarre reason?
For me the game is X-Men Origins: Wolverine. Because the save data is stored inside your profile somehow, the only thing kept in the games folder is the install and I've developed an irrational belief that deleting the game will also remove the save data.
There's my gaming irrationality, do you have one?