These are a few of my favorite things:
1. Urgency For Sex - Begging for it, aphrodesiacs, wanting it so much you can't wait, getting it on in semi-public settings, all that good stuff.
2. Mutliple orgasms - Can't stop, addicted to the shindig (apologies to the Red Hot Chili Peppers). Time after time, better and better, guys or girls who just don't want to stop 'cause it's so good.
3. Alphas - They know what they want, and what you want, and they make damn sure you do what they want. Sexy control and self-assurance.
4. Power!sex - Use of special abilities in sexual situations. Reading someone's mind to know their innermost desires, caressing someone with telekinesis, teasing someone with hot or cold, flight sex, getting all their special abilities into the act!
5. Willing submission - Kneeling because you want them so bad, staying in place, obeying commands, allowing another control over you, getting off on being controlled.
Supernatural: Dean/Sam, Dean/Castiel, Sam/Ruby, Dean/Anna, Dean/Sam/Castiel, or whoever else you feel needs some lovin' in the SPN world!
Heroes: (I like virtually everything about Heroes, but here are a few faves) Nathan/Peter, Noah/Nathan, Sylar/Peter, Adam/Monica, Adam/Peter, Elle/Sylar, Sylar/Claire, Sylar/Luke, Matt/Mohinder, and anyone else you like in threesomes or moresomes!
Torchwood: Jack/Ianto, or Jack/damn near anyone. Seriously. It's Captain Jack.
Star Trek reboot: Any pairing really. They're all pretty awesome. Mirror verse rocks too.