i've done both... depending on my mood: kept riding just shaking my head... or flipped them off...

just the other day... i moved into the turn lane to turn left... the road i was turning on had a stop sign (i didn't).... the idiot pulled out in front of me! good thing i was paying attention.... gut reaction took over: "WTF ARE YOU DOING YOU STUPID A##HOLE????" the passenger's window was open so i know they heard me!