Teemo goes into camo instead of AA
Pretty straightforward and it has screwed me out of CS many times. If you're Teemo and you stand still until just before you camo, then try to last-hit a minion within about a 0.2 second window, you'll half animate an attack, but instead camo out without attacking and probably miss the cs.
Not sure if it also affects targeting champs.
Easy to reproduce, but I don't have video capture software.