Can't remember the title, but there was an episode of the old series where this guy cuts the Joker off on the road. The Joker runs him off the road and tells the guy that he's completely owned now. Then a year or so later, the Joker comes to call in his favour. That episode kicked arse.
And Mad Love. Pure genius.
The Creeper episode. "They call me... yellow skinned wacky man!"
Sins of the Father (that was the one with Dick explaining how and why he became Nightwing, yeah? Correct me if I'm wrong).