One of my favorites, maybe top, is Daniel Day Lewis as Bill Cutting.
He's just an all around badass. A ruthless early New York scumbag who chooses sharpened melee weapons over guns. He plays one of the best roles I think I've ever seen. The way people get boners over how Heath Ledger plays The Joker is how I feel about DDL as William Cutting.
His bad eye, big mustache, huge top hat on top of his greasy hair and his deep bone chillingly vicious voice make him one of the best characters in any movie.
This speech is great too:
The fact that he kills Amsterdam's (leo) father in the opening scene makes him the villian of the movie, but as it goes on, you see that even though Cutting is a no good bullying thief like everyone else, he really almost becomes a father figure to Amsterdam and it makes you sad when he gets
There Will Be Blood was really good, but man I really don't know too much what the hell it was really about towards the end.
"I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg. Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be in the rhgit pclae. The rset can be a taotl mses and you can sitll raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh? Yaeh and I awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins can raed tihs too."
The last post in The Actor Game got me all hot for this one, Agent Milton Dammers from The Frighteners:
He plays a Neurotic twitchy detective who, while doing what he thinks is good, does not know what is really happening and continues to persue Micheal J. Fox who is the one actually trying to stop the murders in his town of fairwater.
This is a great scene, albeit a few spoilers. I suggest watching the whole movie though: