What are the advantages and disadvantages of using an edged weapon; a weapon with a blade, a weapon designed to cut through skin? The advantage is often noted that blades don't need reloading. Pointing to the obvious downside of firearms that once you run out of ammunition they don't work, but blades do need sharpening. If you've ever tried to hit someone with the backside of a machete, or the flat side, you know that it doesn't do very much damage. Also when they are sharp, can get stuck in things. They can get stuck in . . . for instance, this katana can get stuck in a zombie's ribcage or it can get stuck in a door when I miss altogether. The other problem is that they tend to, when they're very sharp, cut indiscriminately, meaning it's easy to cut yourself with one of these, whether when you miss or even just taking it out of the sheath, you can cut your hand. The problem in a catastrophic zombie outbreak is that you won't be able to just put some Neosporin on it, go get some antibiotics, go get it treated. A simple cut can turn into a deadly infection that eventually kills you.
Katanas are often mentioned as a possible ideal zombie weapon, but there are a couple of problems with a katana. One is that most katanas like this one are just made for show. They're ceremonial pieces that are designed to hang up on a shelf or put on a little stand. They're not designed to be used, so they'll actually fall apart very quickly when you start to use them. Secondly, katanas are very long and difficult to use, even if you have a good one. They were originally designed for Samurai Masters who spent their entire lives training with it. Peasants, when they went into battle in that same era, would use a machete because it's much easier to use, easier to yield, and less likely for you to injure yourself with.
Additionally, the bladed weapons are designed to cut holes in things. If zombies are filled with toxic goo that spreads their own sickness around to the rest of the world, in my opinion, the last thing you want to do is start cutting open that bag and letting all that goo come out. Other bladed weapons include scissors, screwdrivers, axes, typical house knives, box cutters, Swiss Army knives. They're all very effective, and have their own uses, but personally, I wouldn't consider them a primary zombie defense weapon simply because there are just too many downsides.