On the "Mike Lips Last Lunch" mission, you must steal Mike's car while he is eating inside Marco's Bistro and rig it with a bomb. When Mike starts the car, the car bomb will explode, killing him. The slogan of Marco's Bistro? "Eat till you explode!"
If you stand in front of a car long enough and they honk at you, Claude will flip them off.
Every vehicle the tank just touches explodes.
Many pedestrian quotes are hilarious.
The police helicopter doesn't have any collision data, besides being damaged by your weapons. You can be on the run and try to avoid the police on the ground, but it won't stop the police helicopter from clipping through the buildings to get you. The fact it stops at nothing to pursue you, even flying through a building, is pretty hilarious.