UGHHHHH! BUT THEY'RE ALL SO GOOD!
I won't pick, but I'll break it down class by class.
Medic: Guy will take care of you. Plus, German. *Swoon*
Sniper: Damn awesome accent. Most likely to be observatory of little details, like what's bothering you, etc.
Spy: The shallow reasons of a relationship would never come to be, because he could become anyone he wanted to. Plus, da 'cat's smooth!
Scout: Energetic, nice accent (again), funny, and he could probably bring in the bacon by selling Sham-Wows.
Demoman: Sexiest bastard EVAR! (Excluding Big Boss) Plus, guy knows how to party with all that booze, and he knows how to blow stuff up. Best weekends I could imagine.
Heavy: Big, strong guy. Knows how to take care of property and DAMN can he make a sammich!
Soldier: Stern, but kind of that bad-boy awesome that his ruggedness just exerts onto you. (Again, Big Boss) Plus, rocket launcher.
Engineer: Real romantic, and knows how to play guitar. Usually I don't go for country-boys, but he seems to be a real thinker. Plus, if the car ever breaks down on the way to the reservation we have, he could fix it right up...with a turret!
Pyro: Only chick. Vaginas are cool. Plus, she shares my love of fire. BURN EVERYTHING. He also must know about safety, because of the rubber suit. And something tells me that she isn't compensating for anything, as he doesn't use any big fancy machine gun or anything.
