Any female gender ... I fuck them before I assimilate them in the collective.  That way all the Borg can enjoy the sensations!

As I remembered the movie Death Wish when Marina Siritis co-starred in it (You know, the cleavage master Counselor Troi), I wouldn't mind fucking her bush with those titties bouncing around.

Betazoid. I always had a thing for Troi. If I could pick an alien from any universe, it would be Chiana from Farscape.