I be male and about half of my characters have been female. For most of my characters, sexuality simply doesn't come up. I think it has only come up for four characters, really. Strangely enough, three of them were female, but I attribute the first two 'frisky' characters to teenage hormones.
My Amazon warrior went wenching once and commented that the priestess of the group had a nice posterior. My Priestess of Bast was most decidedly not picky (only qualification being they were 'cute', regardless of race). My prima-donna bard/cleric of Sune was decidedly against naughty touching, feeling rather adamantly that that would hurt. Finally, though the group’s fighter had the unwarranted reputation for being a ladies man and a partier, my Paladin seemed to get the most nookie of the group (and celestial nookie at that). Course, he was just relieving some tensions when the opportunity presented itself.
My wild mage hit the ‘change gender’ wild surge twice in the same campaign, so it really wasn’t sure what gender/sexuality it was. I adamantly state my fire elemental has no naughty bits to speak of, and thus has no gender, despite being named George.
What has freaked me out a bit in the past:
-Roleplaying the ‘encounter’ (complete with dice rolling to rate the ‘performance’ and xp)
-the wearing of a t-shirt depicting the chest of an endowed female by a male player to remind the DM that he was playing a female character.