Punishment of Silence: She cannot speak in your presence for a period of time determined by you. She can communicate non-verbally, but not through use of words in any form (no writing/typing/charades/etc.)

Cum Restriction: Cum restrictions with any kind of stimulation can be of great use. Particularly when you force her to still please you.

The key to many punishments is not just taking something away, but also reinforcing the desire for it. Making them skip lunch may seem like a light punishment till you cook something that smells amazing and eat it in front of them. The key is: what does your sub enjoy most. The best punishments are suited uniquely to the sub, and while some are easy to share as common desires (almost all subs want to speak, cum and eat during the day), the better you can custom fit your punishment to the crime and the sub the more effective it will be.