These are very much fun to play with and can toss you of your feet mentally. Needles are lovely versatile. I can torture you, give you a mind fuck or use them during a nursing game.
At torturing for instance it can be fun if I push them through your nipples, cock and balls or clit and labia. It directly gives me the possibility to pierce you because a slave is obviously pierced.
It is also nice to make a beautiful patern on your back with a lot of needles. If you are very stubborn I will use you as a pin cushion!
So you see, enough possibilities and I know a few more.