@paniclovesyou -That's not a stupid question, I war with myself over categories all the time :)
So for my advice to help any, you have to know which path you plan on taking as far as the zombie apocalypse. Are you going to be like The Walking Dead and go for Action,Thriller, and Adventure? Or are you going to be like Zombieland and go for Humor, Romance and Adventure? It all depends... You might be making a mash up of the two for which you have to ask yourself: Which one am I going to lean more toward? Humor and Thrillers don't really go together so if you plan to make it humorous I'd make it Humor and Adventure. I know this was a lot more in depth than you were going for, but unless you want to give me something to go off of, it's the best I can do...