My Favorite Is Heath Ledger!
Heath Ledger was deserving but if we are only talking recently I have to go with Javier Bardem as Anton Chigurth in the 2007 Coen brother violent crime drama "No Country for Old Men"..
Talking last half century or so - my first choice is Christopher Walken for his powerful performance as Nikonar "Nick" Nevotarevich in The Deer Hunter (1978)..
2nd choice: Jack Lemmon as Ens. Frank Thurlowe Pulver in 1956's Mister Roberts.
Tell me, who was it you left me for? Was it Laszlo, or were there others in between? Or - aren't you the kind that tells?
I'm not sure about movies but theres a dude called Titus Welliver who crops up in tons of tv stuff. always puts in a good turn.