I always love getting cut off by someone in a brand new sports car. Sideways across 5 lanes of traffic to make a turn, not covering more than 100ft down-track ... and NO SIGNAL!!!! (Most seen in Rockville, MD, and always followed by the comment "Gosh, I thought those new Bimmers'd have turn signals, fer sure!")
Of course, the DC variant of that is to signal yourself in to some impossibly small hole between two cars. It's ok to totally cut people off -- you signalled!
Aargh...