Sometimes a little is much more.

One of my favorite parts of the female body are the nipples. Now we all know there are just skads of delightful things that can be done. What I am going to suggest is both very simple and very subtle. It only requires one piece of equipment, and a bit of time.
My suggestion is to secure the sub on her back in a bed. I like to recline on my side next to her and begin the torment. What is used is a very thin, very sharp needle. Some of the better sewing shops stock fine steel ultra sharp needles. Another place to find them is if a friend has diabetes, the syringes are often very thin and very sharp. It should go without saying the needles themselves must be kept clean. Cheap, disposable alcohol swabs are easy to find.
I know what everybody is thinking. My God, you are going to pierce her nipples! I am sure that is what is going through the sub's mind. Instead I am going to leisurely tease and torment her nipples with the softest of touches, almost like a feather Generally you just very very lightly trace the point of the needle over the nipples and surrounding areas. Take your time, I usually allow at least a thorough 15 minutes foir each nipple The nipples swell and become fully extended. They become hype-sensative. They will remain super sensative for several days afterward. I enjoying timing it right before we go out on a big date or to a public meeting. I also delight in working her up right before she has to go to the office or job. I like to insist she wear either a shelf bra, or a bra with the tip cut out. Silk, satin, lycra, or other stimulating fabrics are preferred for tops. For a well disciplined sub, it is great fun to not tie her to the bed but command her to remain still during the slow process. If she squirms she is punished.
On the theory if it works one place it should others, I have tried it on the labia and the clitoris. The labia generally works ok, but the clit is just so sensative, it usually doesn't give the desired result. The general feeling on the nipples is an intense and maddening itch that can last for days.
Feeling medieval one night, I decided to heat the point. I used a thin candle and had her navel as a candle holder. Every time she would squirm, hot wax would drip down onto her very tender tummy. The hot needles didn't leave as much of an itching sensation, but it certainly offered other compensations.