Joker cutting Two-Face's wrist open with pieces of shrapnel already stuck in his fingers. Talk about Crazy-Prepared.
Oh, and Harley Quinn's part in the same scene - ambushing Two-Face and his thugs by disguising herself as a gorilla.
Two-Face refusing to take the Joker's call. It may have been just the luck of the coin, but his smirk says that he knew it would rile Joker up. By extension, he got the Joker to Freak Out, kill one of his mooks, burn down his strip-club, and cry like a child in an alcohol/pill-laced stupor on Harley.
Batman, with only three words, shows that he can torment the Joker just as much as the Joker torments him.