Magic resistance doesn't help you resist a 5m radius snowball getting dropped on your head.
Edit; Or wave gun, Under Five meters with no metal head armour = 1 hour of sleep + migraine and a slight amnesia. Either one works
also Question; How will raule (who's been chatting) Work out which student threw a snowball in his direction now that a mass snowball fight seems to have broken out + get over to said student without said student spotting him, Its not like a snowball is a close combat weapon. And anyway, we're assuming it hits Raule, what if it hits the girl pestering him?