I thought the funniest part was when Batman plays chicken on his bike with Joker's truck (wrapping wire around it and right before it flips over) and Joker says "he missed!"
I was the only one that laughed when joker was telling Spawn about his scars. He looks at the black guy being held on the ground and says "why so serious?"
After Dent tells rachel reservations took 3 weeks to get at the restaurant. bruce comes over and says to put 2 tables together, Dart says oh we can't do that here or something like that and Bruce says oh i own the place.