Role playing is my favorite. To become immersed in something is very exciting. I'm a switch and like different scenarios but usually ones that start out with one person in control but end with another. Or where there is a power struggle. My favorite that i came up with was:
I'm a master who was spotted by a Dom. She decides that I'm her pet project to turn into a slave. She sneaks into my room when sleeping and puts a chastity device on me with a note to meet her at her dungeon. When I get there, I naturally return the favor by putting a wireless vibrator on her (the one found actually fit like a harness and I could make it pretty snug), tie her legs tight and put her in some bondage. and tell her it's not coming off until she gives me the key for the chastity device. Then the battle of wills ensue. She tries to get me as hard a possible so that I'm in agony and I'm driving her to constant orgasm until she can't take it. Add in a little anal play and you can imagine where this goes.
I've won a few times and lost a few times :-) either way its usually lots of fun.