For those with a fluent tongue, a very interesting form of power exchange rarely discussed is when a Top/Dom(me) speaks in a different language (presumably, one not know by the bottom/submissive), where the dynamic starts to take into account things like body language and intonation.  Great fun for a "captured by the enemy" interrogation scene.  And, if you don't speak a second language, maybe just come up with a gibberish language like Andy Kaufman once did?  

I DO know lots of curse words and insults in other languages. LOL  This is a good tip, and one I'll definitely incorporate into scenes in the future.