Khajiiiiiiit!
To be honest, anything wearing Nightingale Armour will look very, very scary. Yes, even an Orc or an elf; as long as the race doesn't have a tail, once they wear the armour they're practically anonymous.
EDIT:
The best assassin is one that does not look like an assassin.
True, but I doubt the OP's gonna walk around in chef's clothes just to be realistic. Or maybe he might... would be fun to try.