Seriously? A vibrator. Not the big, goal oriented ones you first think of, but a small, powerful, easy to use with one hand kind.
Because a nipple clamp is fun. But a nipple clamp with a little vibration? Zoom!
Tied up his cock and balls? Try running a vibrator across them. Teasingly.
Bound across the bed? Could be fun. Bound across the bed while your partner alternately teases, pleases and tickles with the vibrator? Awesome.
Don’t use it with a goal in mind. Use it as a sensation. Run it across the inner thighs. The soles of the feet. Down the ribs. Across the top of the scalp.
Use it to tease and deny.
Keep in the the fridge on a hot summer day.
Do make sure to keep extra batteries close by – and if you are going to store it for any length of time, take the batteries out. To clean it, wash with anti-bactierial soap.
I would recommend something like Shivers – pictured here, or something simple like the Iconic Smoothie, or the more expensive, but totally fabulous Little Chroma. (Clicking on these links takes you to Eden Fantasies, where I am an affiliate.)
Thank you to Crippled Girl for the question!