Credit: The CW; HBO; The CW; ABC

For every happy, stable couple on TV there’s a sexy, passion-fueled hookup that makes steady-as-she-goes monogamy look super boring.

From Chuck (Ed Westwick) and Blair’s (Leighton Meester) hot-’n’-heavy limo ride on the first season of Gossip Girl to Castle (Nathan Fillion) and Beckett’s (Stana Katic) makeout sesh (and more) on the Castle Season 4 finale, these small-screen romps are full-on steamy — often because they’re long overdue. (It’s one of the most basic laws of TV: If you can cut the sexual tension with a knife, the first time will be smokin’ hot.)

Now it’s up to you to make the tough call: Of the following hookups, which was the sexiest?