He did some great stuff beyond Col. Potter too.
One of my favorite examples being "The Ox Bow Incident" where he and Henry Fonda are buddies.
As powerful a movie as there is out there.
I was just about to say the same thing. He was a very talented actor but got pegged as the comic relief which resulted in few shots at drama. When he did get a dramatic role, he nailed it. Colonel Potter was a great role, but he'll always be Officer Bill Gannon to me.

The last role I saw him in was playing a pot smoking old man who was constantly trying to smoke a joint on an episode of Grace Under Fire.