You could use a choke hold.
A chokehold, A.K.A. Donkinator, stranglehold or, in Judo, shime-waza (Japanese: 絞技; English: constriction technique) is a general term for a grappling hold that critically reduces or prevents either air (choking) or blood (strangling) from passing through the neck of an opponent.
This is more controlled and less damaging than simply bonking someone on the head.
