wow I  would have a couple of choices here hmm and for differant reasons !

I would have to say ally moore is one of the best round full backside for a real hold on for your life ride

erica formerly of tbd has the pear shaped droped apple but that is so sexy

and crissy from tbd has a little perfect but that I just had the pleasure  of grinding against and she can move it just so well

just my 2 cents

Jasmine Fine has an awesome ass.  Check it out the next time she is in town.