I read the zombie survival guide and while it was amusing, it was pretty stupid. They say zombies have super hearing so you should use a suppressor. If their whole body is a decaying corpse, what the hell would make their hearing improve?! They also used "clip" instead of magazine when refering to the M1 Carbine use during an outbreak.
M1 Carbines are a great choice... 30 years ago, back when ammo was available. A Ruger Mini-14 is almost the same thing in a more readily available caliber. Not super accurate but effective enough. I have one handy so I'm set for the zombies.
A good sniper rifle, even a .22 would work well on zombies if you were in an elevated position they couldn't reach. Take your time and rack up the head shots!
I'd like to think zombies are what everyone usually thinks of, a slow moving, stupid corpse that moans and can't sprint. I'd hope only a bite would contract the "zombie virus", as it is hard not to be touched by zombie blood. As MPM mentioned, everyone has their own ideas. I'm making a zombie movie this summer, I'll add caps from it on my profile (and try to use as few airsoft guns as possible!).