Wild Things had some hot tension between Denise Richards, and Neve Campbell during a three sum with Matt Dillon why there wasn't a great knock down drag out catfight between the two has always pissed me off ! As the atmosphere was very dark and in a swampy area, they could have easily used two stunt chicks grappling in some dark goo ripping tearing biting rolling
Deviant Motives has two chicks arguing about which pussy the guy likes better in a threesome.
The Girls of Cell Block F has two chicks fighting over giving a blow job
Pushed is nothing but catfights during threesomes
Attention Whores (I think the first one) has some really good rivalry in a threesome
Lastly, I accidentally found the best clip ever on lime wire one time. I think it was German, but it's an orgy scene with a chick on the floor giving a blow job next to a chick getting banged on a table. The girl getting fucked started getting rough with the the girl giving the blow job, so once her mouth is full if cum, she gets up and spits it on the chick getting fucked. Right in her face. Then starts rubbing in it in. The girl getting fucked starts hitting the blow job girl and then some other dude starts banging the blow job girl from behind. Both girls start cumming. And that's when the clip ended. Hottest clip ever and I could never find it again.
Good luck in your travels.
There's another old porno called the Artist, I think. Two chicks first each other in a fight over a dude at the end. Very hot scene.
It's out there, you just have to dig for it. Hope this helps. Hey, if you find links to these, post them up!
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That orgy scene was totally amateur, by the way. Looks like it was filmed in a club. Seriously, if you ever find that clip, that's your end state in this search of yours, guaranteed! Post the link.