He was a very funny guy. I know him mostly as Super Dave, and I had stopped watching Curb Your Enthusiasm before his character, Marty Funkhouser, joined the show. In one of the tributes they mentioned this scene from Curb in which Marty tells Jerry Seinfeld a joke. The cool part of the story is that the only thing in the script was "Marty tells Jerry a joke," so nobody knew what was coming, and Seinfeld's reaction was genuine.
The punchline is very dirty, LANGUAGE NSFW, but I guffawed.
His G-rated comic character of the late seventies and early eighties Super Dave Osborne was hilarious. He was a mini-icon with a cult following. His main schtick was his character would do dangerous special challenges or movie stunts that went wrong. Between the routine itself the characters personal mannerisms and the way he spoke just made everything work.
Here is one of my favorites and very representative of Super Dave Osborne.