With all the people gaming naked, I'm started to get worried that I'm wierd because I game clothed...
As for wierd stuff; neat bases, hoarder of items with sentimental value, compulsive ordener of inventory (in games like Baldur's Gate or Icewind Dale, one person gets all the arrows, the other all the weapons, the other all the scrolls, etc) but worst of all is the compulsive merchant.
I take anything that has a selling price. One copper piece for a 50 pound rock? It's sellable, take it. When I'm stuck in the wild with a full inventory but find a good item, it's math time. Amount of gold pieces per pound is the thing to keep into account here, and I can spend 10 mins easily reorganising and making inventory of my inventory so I won't lose an item that could've given me a goldpiece more profit (though going on adventuring and making profit in that time would be more efficient). Old Dutch habit I think. It does allow me to name the item cost for a ton of items in a bunch of games (Morrowind, Oblivion, Baldur's Gate, Icewind Dale, The Witcher) from the top of my head because of hours agonising over them.