OCD things you do in games.

[Mass Distraction]

Collecting every collectable I see.

Trying to keep all NPCs alive in whatever game I play.

Reloading after only a few shots.

If I find a new game I might like I just have to buy and/or play all the previous titles before getting to the new game.

Saving again if I don't see/hear the game actually getting saved.

In RPGs I always have to have at least one of each item. This has led me to impossible journeys to find the rarest ones.

Saving in a specific spot. For example, in Pokémon I have to leave my character so that he won't block any doors and is possibly in a corner of some kind.