It's hard to say really, I've had a level 51 Metapod back on Pokemon Blue, whose only move was "harden", that was more of a waste of time though. I collected all of the orbs in Crackdown 1, when I was nearly maxed out in all abilites too.
Most recent one I'd say is "stealing" all of the Gold Bars in Fallout: New Vegas: Dead Money (DLC), traveling by foot halfway around the wasteland, which took ages by the way, then never to actually use them in any shape or form. I've also collected one of each gun, item of clothing, etc and put them away in individual containers. (Misc, guns,etc.)
Same goes for Skyrim too, even got myself a shit ton of gems and ore for no reason at all.
Could be a case of video game Obsessive Collecting Disorder, rather than Obsessive Cleaning Disorder though. Or just a mixture of the two.
I've also played Angry Birds.
"If anyone is singing a musical number in this house it’s me!"