I'm certainly not knocking anyone already mentioned, but I always thought the Squire of Gothos gave a very entertaining if somewhat campy performance. Sort of had a 60's/Batman vibe to it, he would have fit right in there with Adam West's rogue's gallery.
I just can't recall the actor's name off the top of my head but wasn't he in "Strangers on a Train"?
William Campbell ("campy" performance LOL)
Also liked the actor who played Flint (James Daly) in Requiem for Methuselah, don't know what else he's been in.