LSD.
Not tried it but sounds pretty amazing, there have been a few threads on how super-sexual-intense-yet-spiritual it is!
that sounds like it would be weird! to me at least...
Ooookay there's been a more recent one in EADD but I think it was just part of another thread so can't find it - but this one maks it sound pretty fuckin' awesome!

Here is another thread in Psychedelic Drugs about sex on hallucinogens/dissociatives..
(ketamine sex was just icky IMO but hallucinogen sex sounds full of win, tis on my list of things I must try :D )
