Casa's choice of clothing in Snappy Dresser: diapers.
Salvatore & Maria bickering in Contra-Banned. This line sums it all up:
Salvatore: Fuck me?! Fuck you! In fact, everyone has!
A cutscene in The Guns of Leone, right before the fight.
Sindacco member: Hey, someone dropped a dollar!
*gets run over by Salvatore's car right after crouching down to pick it up*
The final cutscene in Bringing The House Down, with literally everything exploding. The best bit is when a blown up car falls on top of two Forellis, killing them, and the other Forelli who was next to them but didn't get hit starting to run away before being crushed by yet another destroyed burning car falling on his head.