I try every now and then (read: all the time) to kill one or two people in front of cops then lose the wanted level and start again. So much fun.
Another lucrative time-waster: Hijack a "Gruppe 6" security van and drive to a remote location, then throw a grenade under it.
The amount of money that comes out of it would give you a nose bleed.
Then try to pick up as much as possible until the police arrive - for some reason the cops aren't fond of grenades.
Dodging bullets + Foraging Green = Hilarity.
