Plak / paddle
For starting SM lovers this might not directly be recognizable but the word paddle or, to put it differently, rowingcane will ring a bell I suppose. Now, these beating instruments look a little like that but are a little smaller in size so they can be handled easier.
Should you want to try this at home with your partner, buy a tabletennisbat because these are well suited fort his. Do start carefully or else the fun will be over quickly.
The feeling this will give on your buttocks differs with every other beating instrument, but one thing is for certain, I will colour your behind into shiny red!