Zenith. But you can't romance him
Quinn. Smart and hard to get. Makes you wait for him,and then keeps you wondering if all the romance was a ruse. Definitely, gives you a roller coaster of emotions.
Iresso (customization 7 works for me). That part when he locks you on the ship for some 4 hours 34 minutes for recreation... And people complain that he is boring. Wake up!!