But say I'm doing a project in Java and they are about equal, I keep giving Al the meaty work then use it justify a promotion, which I can't justify for Marcy. It's not that she's that much worse, I just never gave her the chance to prove it (blah blah peter principle, perform at next level, etc...). That just might be a bit sexist.
Have you really never worked on a project where the golden boy was the face of everything and everyone else was ignored?