"The Battle of Evermore" Led Zeppelin (good luck with that one)
Yeah, I guess that's not exactly a dance tune.
How about
"Summer Nights" from the musical
Grease?
(Musicals are actually a great source for male/female duets as long as you can put up with a little cheese factor. I did a little googling and it seems that stuff like "Endless Love" and "A Whole New World" are popular, especially with women.)
I've also done (with male lead and female harmony)
"Bye Bye Love" by the Everly Brothers.
But if you're just talking about one of the two voices singing harmony then the list is pretty much endless as almost any song with BGVs can be arranged for male/female voices.
Back to "true" duets, here are some others that you may or may not want to rock up:
"Opposites Attract" Paula Abdul and The Wild Pair
"Ebony and Ivory" Paul McCartney and Stevie Wonder
Top 10 Male-Female Duets of the '80s (about.com)Male/Female Duets - Rock (LetsSingIt.com)Seems to be a lot of Johnny Cash/June Carter fans out on the net, too. More fodder for rockification (or not).