Depends on how far you want to take it... Tried animal role playing? Being a dog/kitten/rabbit or whatever, getting taken around on a collar and leash etc... There's also rape-play, prisoner/prison guard, doctor/patient, master/slave. Anything with an inbalance of power will do the job I suppose. A good place to pick up kinky ideas is fetlife.com. Shibari has caught my imagination recently, it might be worth giving that a look if you like bondage-type stuff, but whips/handcuffs/blindfolds/ball-gags are still the kinky classics.
"... Tread softly because you tread on my dreams"