A lot of the dudes mentioned so far are sick, here are more:
John Oliver:
Demetri Martin:
If you like Mitch Hedburg, try Steven Wright:
Norm Macdonald (his act begins at 2:45):
(After posting Norm I feel like we did this before and it turned into a Norm Macdonald appreciation thread)
Andy Kaufman (more than a stand up, but hillarious. Love or hate kind of guy, nobody thinks he's just ok)
Also, is anybody watching Last Comic Standing this year? Never really followed it, but have been this year. This dude has been making me laugh:
And that guy who was in the king of queens and the comedians of comedy sucks. It feels like its like an hour of him talking about how much smarter he is than everybody else.