I first saw Patton Oswalt when he was on the Comedians of Comedy. The episode where he stuck out was when he went to the comic book store on new comic day and he and another comedian had a long discussion of comics.
Doing some research into the guy led me to his stand-up which I found out was full of great geek material. Aside from having great stand-up, he appears all over television and the internet. He was Constable Bob on Justified and he had the funniest Twitter Trolling of all time.