Cliff: Jean Grey (in my icon)
Firstly, she's proven in the past that death (including death by falling from a great height) is no obstacle to a shag. Secondly, I think she'd be absolutely awful to marry - the temper, the telepathy, the running off with Logan and/or Emma at the drop of a hat... Definitely CLIFF for Jean!

Shag: Zoe
Now, you might think that Zoe is the marrying kind - she's loyal to a fault, keeps her friends around for years on end, and, of course, got married. The thing is, I don't think she'd leave her captain - to marry her, I'd have to be willing to head off on Serenity, to which I would say a polite "No, thank you!"
Marry: the lovely Wendy Watson! (in this icon which I stole from
Wendy has a cool apartment, loves art and video games, already has a terrific girlfriend who would be into non-conventional relationships (not to mention sexy dreams about Pip!), and is generally an entirely awesome person. Also, I don't mind her boyfriend. Yes, Wendy keeps odd hours and dramatic secrets, but nobody's perfect. And, of course, she recycles. Avidly.