Things that make me breathe hard always seem to involve control. Breath control, for example. Taking her by the throat while looking into her eyes...god damn. I've done this in a bar, although I don't reccomend it. Lying on top of her while she tucks her knees in and compresses her chest, with or without fucking her at the same time. Kissing her while performing an assisted front naked choke using her shirt. Power games. I've never liked rope or cuffs - it's much more debilitating and intense if she stands still and squirms and holds eye contact while I do things to her, knowing that she can move away but feeling like she just can't. "If you move, I'll stop." Statue games. Blindfolds, although I do things with eye contact and a soft voice that I probably shouldn't. There's more. These sprung to mind.