Baking sweet things, I always end up picking the wrong kind of sugar or unbalancing the mix enough to leave a curiously chewy layer over the top of brownies, or unexpected lumpy bits in butter icing.
USB ports big time, and plastic wrapping - games & cigarettes get me, especially since about one time in three I discard the finally-defeated wrapping on the carpet and end up nearly slipping and cracking my skull open. Moreso the packaging around small electronics and other things the manufacturers clearly don't want you to get in to. Normally I resort to scissors, but that just paves the way for plastic cuts.
Oh, and even though I'm pretty in to my games, I kinda suck at them. Not too good with figuring out puzzles, easily lost in anywhere that isn't a straight line, terrible coordination for rhythm games and paranoid, panicky & prone to fits in anything that requires accuracy - even moreso when it's coop and people are depending on me being even a little bit competent. I still have a lot of fun, though.