I think one that always jars me is 'trainers' instead of like, sneakers or something.
My majour problem is that I was raised in England and America, so I'm all colours of confused on what is or is not slang for which particular country. *facepalm* Add to that, my dad is american/italian and my mum is northern english, so I have all kinds of weird slang going on.
American slang-specific beta's are the best.