Deanna Troi (Marina Sirtis) always got me going and I've lost count of the number of times I've spilled my load over her. Awesome woman, very very sexy!!
jadzia, troi, crusher, in that order. then 7 and torres. enterprise never happened (it sucked, despite hoshi). i'm not sure i like the new movie... lots of mindless action and a story that makes no sense (it is jj abrams after all, so i wasn't expecting much) but there is no trek feel in it.
Deanna Troi (Marina Sirtis) was my first Star Trek crush, and so she'll always be at the top of any list. That and she was just hot in the series -- and apparently still very much so if that above picture is any indication.:drool2:
Jeri Ryan would also be on my list. That skintight Seven of Nine outfit filled my teenage brain with some filthy thoughts. Definitely one of my favorite instances of fan service ever, and I still give thanks to the Star Trek: Voyager producers for that wardrobe decision.
I'll give you an obscure one: in the finale of Voyager, we saw the future for the characters, where Paris and Torres's kid was fully grown. She was 1/4 Klingon and the actress was gorgeous. But I have no idea who it was.