I had a brief fling with a girl that was into masochism. I'm not really sadistic so it didn't work out (among other reasons). But I would suck really hard on her clit. Almost stretch/pull it. I would only do it every once in a while, but everytime I did she would go crazy (in a good way). I would also very firmly hold her thighs and squeeze her ass. Much harder than I would do in general, but she would ask for it: "grip me harder" she would say. Also, periodically I would reach up and slap her breasts and tits while going down on her. She loved it...

I'm such a freak. I kind of want the challenge of having you feel pleasure from me going down on you now. I'm not hitting on you or anything (it's just hypothetical) and I'm sorry if I'm being forward/rude/inappropriate.