I've just thought of another candidate: Shannya Tweens (aka Tweeks, Tweaks, or Twain).
This French starlet comes across, on first appearances as an attractive brunette with sultry, supermodel-esque good looks and a gorgeous curvy body that is framed by a pair of butt cheeks that look like a well-formed Dutch cheese. She's the sort of girl that I could imagine would have a lot of straight women toying with the idea of lesbianism.
Once onscreen however this Gallic lovely transforms into a fiery strumpet who loves to engage in the sort of violent encounters that would probably have Max Hardcore at his most aggressive thinking that she's gone a bit overboard, and needs to ease up a little.
Shannya has a butt-hole that would make a glove puppet envious of its capacity to consume an entire arm. I don't think I've ever seen another brown-eye open up so easily to allow itself to be double - and even in one glorious scene - triple-penetrated;
She squirts like a vigorously shaken beer-can, and can hit a camera lens yards away, usually when some lucky guy has his hand up her ass and is cranking her like a vintage motor car.
She appears to be devoid of a gag-reflex judging by the way that she can easily allow a cock (or two, or three) to tickle her stomach lining without losing her breakfast. And if there's another girl who can nod her head during a blowjob faster than Shannya without suffering whiplash then I would certainly like to make her acquaintance;
She also has the flexibility of a Olympic gymnast and twists herself into the most uncomfortable looking positions to allow deeper and more intensive access to her receptive orifices: handstands and anal anyone?
She's also not averse to doing a bit of bondage, for those that like that sort of thing, not my bag personally but even I can see the appeal of having this girl tied up and at the mercy of a group of angry men.
All this, and what appears to be a genuine pleasure in her job, coupled with an unhealthy appetite for cum, cock, ass-mucus, pussy-juice, throat goo, and whatever other fluids may pass her lips make this girl one hell of a contender for porn's filthiest women. What really does it for this shoe fetishist though is her delightful reluctance to take her heels off. Even when allowing herself to be fiercely violated in an extreme scene involving multiple studs hammering every tiny gap they can find in her body to squeeze a cock or a fist into, and when the studio floor must be dangerously covered in lube and slime of her own making, Shannya will usually keep her heels on. What a girl!
Shannya looking cute:
http://imagenes.cumlouder.com/reventandoculos/rc10/pics/fotos-900x600/foto1.jpg
Shannya doing what she does best:
http://www.assholesurfers.com/shannya-tweens/video02/pw.htm
Shannya looking cute AND doing what she does best:
http://galleries.rebootcash.com/explicite/cc=1136665/tp=53/shannya1/