Last night a Ravens player was ejected from the game, and the Ravens were penalized, for "punching a player in the facemask."
They say virtue is its own reward. Likewise, I think punching someone in the facemask should be its own penalty. If you're dumb enough to think you're going to harm someone by slamming your fist into the stout metal cage that protects their face, then you should just live with the broken fingers and your team should be able to carry on without you.
On the other hand, I firmly believe that the NFL rule against "using a helmet (not worn) as a weapon" should stand.