The bayonets main purpose was for use after you ran out of ammo. Or your weapon failed. Hand to hand type stuff. Mostly because it was just way more efficient to just shoot'emface stabbing? stupid.
You're supposed to go for the guts not face(the face is nothing but bone). also that is USELESS for anything but combat or fish spearing(as trav said). bayonets were used for a reason, more than one or two possible uses.