Alistair, of course. My goofy but ultimately strong idiot of a husband (I always let him kill Loghain, it's only fitting). Although I did dally with Zev, I always stuck with Alistair. My first playthrough I didn't know about getting Morrigan pregnant, so when Alistair died I freaked the hell out and reset and looked it up. I still agonized over letting Morrigan and him sleep together, even considered letting myself die in his place, but I couldn't do that to him or my friends either so I let Morrigan have her way because I wanted my Alistair.
Leliana had a thing for me too, but she annoyed me.
I've done so many playthroughs but it always ends up: Stay friendly with Alistair, play with Zev as soon as he shows up, then dump Zev and move on with Alistair.
Yes, I get my cake and I eat it too. I get a little too involved with that game.