Shillelagh

This spell enables the druid to change his own oaken cudgel into a magical weapon which is +1 to hit and inflicts 2-8 hit points of damage on opponents up to man-sized, 2-5 hit points of damage on larger opponents. 

The druid must wield the shillelagh, of course. 

The material components of this spell are an oaken club, any mistletoe, and a shamrock leaf.