In a world full of Zombies, a big knife might make an effective last ditch weapon. When people fight zombies in the movies or on TV, they usually use firearms or chainsaws. But, when you are eyeball to eyeball with slimy rotten Zombie don't underestimate a good knife. You can usually reach and deploy a knife fast and you don't have to fumble with safeties or sights. The knife is a very instinctive weapon that everyone knows how to use. It can re-kill a Zombie outright or can deny it mobility by cutting tendons and other vital parts.
I've got two big hunting knives that just might do the job against a Zombie in close quarters combat. If a SHTF-scenario comes up, it's reassuring to have a good solid knife readily available.