ya i was getting bored as hell with SA till i found multiplayer, just having another human with unpredictable actions running about you is entertaining.
now that ive played 4 i cant go back to SA...love the gta4 car physics too much!
what ive done:
pull random people over or wait at an intersection for an idiot driver to do somehting then pull em over. "ticket" them by shooting em then running away lol.
evil swingset is always fun, someone pulled me outa my car as i was driving up the swing and the car rocketed off by itself but the door clipped the guy that pulled me out flinging him too.
stealing a semi/bus and driving as fast as you can thru town, or just speed thru town and tbone a car then get out and survey the damage(damage physics rock!!)
or try to land on stuff /stunt is always fun
i dont bother too much with the 100% either, like you if i see one ill grab it.
i do enjoy collecting cars for stevie tho