I think my all time favorite was Alexander Pope's model on season 12, Ji Young Baek.

I also loved Raymudo's model on season 2, Allison McAtee. She didn't make it past like episode 3 and every time she walked the runway she was wearing an insanely terrible look (she has the unfortunate distinction of wearing the infamous "barefoot Appalachian Lil' Abner Barbie" look).

Honorable mention to Tara from season 2 for being in the center of controversy when Zulema poached her from Nick Verreos, who then suffered from creative block when he didn't have his muse.) Aaaand Melissa from season 1 who was only 17 years old and wore that swimsuit to a Page Six cocktail party for part of the challenge and totally flirted with all of the old guys there.