Names. As some have already said, I am also horrible at remembering names.
It's very awkward 90% of the time. Usually it happens when I meet new people at parties, and with my luck I also often bump into them at Uni or someplace and they'll be like: "Hey you, remember me?". "Sure, I'll say" with no clue.
Another thing is that I bring home stuff from work. When I was restocking supplies in the grocery department, I had a phone I took home, and now I sometimes bring back shopping carts into the store. To do that, I need a special key to unlock the carts, and that key is also prone to be taken home with me.
My employers always makes fun of me for that.