Wooden paddles... I do love a good wooden paddle for a good solid thwack! The ones that are my favourites are with holes in them so that there is no air cushioning and you get an even mightier thwack.
I have two thick wooden paddles, one with a rubber strip down it to make it worse! Then I have various thinner wooden paddles too, a long thing paddle and a flat oval ended paddle & more. I also have a selection of leather paddles for those who aren't brave enough for wooden implements!
See some of the bottoms I have paddled on my Bottombook.