If I picked from TWD, I'd take:
Carl (an excellent shot - dead or alive, Carl will plug it)
Michonne (baddest badass on TWD)
Rick (has leadership experience and can kill walkers)
Tyreese (kind-hearted, handy with a hammer and hot)
Judith (because Tyreese ain't going nowhere without that baby)
If I picked from other shows/movies, I'd take:
Buffy Summers (she's super strong, experienced with kicking undead ass and would adapt easily to staking them in the brain)
Spike (he's undead, likes to kill people and the undead and he's hot)
Dana Scully (she's a doctor and a cop and has experience with the undead)
Fox Mulder (he'd figure out the government conspiracy that caused the walker outbreak and he's hot)
Noomi Rapace's Lisbeth Salander (she's a freaking fierce genius who would scare people - and maybe even walkers - away plus she'd probably get the computers going)