Well, as you can tell from my name, I'm partial to the ladies from Penthouse. There's a number who stand out, but overall I'd have to go with
Ginger Miller, the 1989 Penthouse Pet of the Year (sorry, I can't post any pics on the wife's computer!

)
From 1989-1992, Penthouse really had some hot-looking Pets of the Year. Ginger Miller, Stephanie Page, Simone Brigitte, and Brandy Ledford were all
stunningly gorgous as well as hot-looking and sexy. I was never that impressed with Playboy's PMOY's, but I doubt any quartet could match those 4 awesome looking ladies. Ginger's pictorial in particular is awesome; one shot of her frontally nude with her head arched back and eyes shut is indescribable.
As good as Ginger looks in her Pet of the Year pictorial (I think some of her photos are up on Penthouse.com), she doesn't look as hot in her Pet of the Month shots. Seems to be the pattern with alot of the Penthouse ladies from yesteryear, when the magazine was still great.
But check out Ginger in some T&A vidoes:
Gellorama, Foxy Food Fight, Wild Bikinis, Best Chest In The U.S., and California Girl Bikini Contest #3/#5 -- she looks super-hot in these videos, maybe even better than in her Penthouse pictorial. I think she looks best in Gellorama and FFF -- literally busting out of her bikini top in the latter and doing a sexy striptease in Gellorama.
As for her ass, the word "flawless" comes to mind -- if you don't believe me, check out a closeup during her routine in "Best Chest In The U.S."