An odd one, my own twisted mind
 

Used for punishment or otherwise: Have a rather long paper, doesn't matter what it is really, just make sure it has lots of writing on it (Things like "I will do as master says" on the paper would work best). Have your slave bent over something (insert butt plug, apply clamps, whatever will really make them want to cum). Begin to rub their genitals and tell them they cannot cum without permission and make them read this paper to you, any crack in their voice, missed word, moan, etc. then they must start over. Maybe recieve some punishment for it depending on how harsh you're being. Your choice to let them cum at the end or not.

Taken a step further by making them copy it to another piece of paper afterward whilst being fucked (strap-on or otherwise) and still no cumming until finished and legible. Can't fuck them too hard though otherwise this one's unwinnable, because you will be moving them to much for them to write it , unless that's how you want it to be.

Could also be done with enema, must read entire paper without cumming or spilling a drop or recieve punishment.

This sounds like fun :D I'll defiantly do this one sometime.

I like it. Sounds Fun!