There are only a few comedians that have made me laugh and think. One of them is George Carlin. Here is a video of the first George Carlin routine that I remember. Don't press the play button on the video if you're offended by profanity.
There are other classic Carlin routines such as The Ten Commandments and the Seven Dirty Words. I have to smile when I think of him, Richard Pryor and Lenny Bruce holding court in the afterlife. It was sad learning of his transition yesterday but I'm glad to have witnessed his genius. May he rest in peace.