The rules are simple - or perhaps I should say non-existent. I think a couple of examples will suffice:
Barry ("The Neck") Nelson
Sean ("Tats") Connery
George ("Who?") Lazenby
Roger ("The Brow") Moore
Timothy ("Heathcliff") Dalton
Pierce ("Pain Face") Brosnan
Daniel ("Pecs") Craig
There are plenty of characters, actors, directors, etc. to choose from - including alternates for those already listed.
Have at 'er!