2 hours ago, Bill W said:

And so was the silent film star Buster Keaton.  He was a genius at deadpan humor.  

He came to mind first for me also.

Leslie Nielsen was so good at it I find myself looking for punchlines in his earlier dramatic roles.

5 minutes ago, JamesSavik said:

Ben Stein did deadpan brilliantly.

Pat Paulsen too.