I would love to see a little more dynamic world. NPCs are always passive.
What if NPCs get a pissed off meter. If you bump in them hard, they have a chance to start a fist fight.
If you crash in to a car, or do a lot of damage to a NPC in a car, they get chance of trying to ram you, or start shooting at you.
More or less as you got in GTA San Andreas. Where you could cause a incident, by provoking NPCs.