John Cusack, Amanda P- oh, wait. That's been done.
Let's see...
The Dalai Lama Tenzin Gyatso - he'd be the fun-loving member of the group, possibly with his own catchphrase.
Chuck Norris - he's in the ass-kicking business, and business is good.* Not sure whose ass he could kick in a post-apocalyptic world, but whatever.
Stereotypical Black Guy - obviously he would need to say "Aw HELL no!" and "Dayum!" as much as possible.
Jackie Chan - because the world needs martial arts... to hunt for, uh, food. Yeah.
A Grizzly Bear - would act as the lovable non-speaking pet. Sgt. Hugs or Commander Claws are appropriate names.
Simon Pegg - 'nuff said.
Simon Pegg's Partner - even gods need company.
Claire Forlani - 'cause she's hawt :3
Myself, Twice - I assume cloning technology will be available prior to Rapture, and I couldn't think of anyone else.
*Someone gets a cookie if they tell me what that quote is from.