With the exception of Tom Selleck, I'm struggling to think of another actor (male or female) more defined by this particular facial hair than William H. Macey.
Come to think of it, that "H" is a bit of a gimmick as well. If he was just clean shaven William Macy, I doubt he would have had the career he has today. Has anyone ever owed so much to so little (facial hair)?
Hmm. I dunno, I can accept Macy without his moustache - in fact it looks kind of out of place when he does have one. The H, yes. There was, of course a well-known actor called Bill Macy and I assume he used the H to distinguish himself from the other guy.
Selleck, yes - without it he looks naked.
I'd add Sam Elliott - most definitely an actor defined by his facial hair. A while ago I watched The Contender and it was really jarring seeing Sam without his 'tasche.