My rubber soled slipper. What a lovely noise it makes when it lands on a naughty bottom! I love the fact it's a good implement that I can be wearing all the time inside the house!
Being a school Headmistress and having to punish naughty teachers and schoolboys, I especially like getting them over my knee, with their trousers down and spanking them with my slipper for a lesson they won't forget.
See some of the bottoms I have slipper spanked on my Bottombook.