If they invented it id say a gravity hammer XD
pros: It smashes anything near you. Will kill zombies instantly. Good when cornered. Good for crowd control.
Cons: nothing absolutely nothing cept you can only use it 10 times in halo 3 but other than that absolutely nothing
I must respectfully disagree with the Katana as a weapon. Despite my own love of them, the sword as a whole is less effective as a weapon as one might initially think. In reality, the sword, while successful for thousands of years as an infantry weapon, was effective against other, living human beings. Essentially, humans feel pain and when a part of their body is injured theree are a variety of physiological affects. In melee combat where swords were use, it was not that common for heads to be taken on the battlefield since while you were prepping for a kill stroke somebody else was putting another sword through your ribs. ZACH on the other hand, could give a shit less about pain or even a lost limb. He just keeps coming and coming. In my opinion, a weapon that can do heavy damage quickly and have an even faster recovery is best. A crowbar, mace, baseball bat, etc. will be much more effective than a Katana.
Generally, you're going to want to keep your distance from the target. And given the fact that a zombie is a walking bio-logical accident waiting to happen, I recommend it. Guns are your friends. However, use them modestly. You never know when your really going to need them most, and trust me...you don't want to be cornered only to find you're out of ammo.
Familiarize yourself with various weapons, long and short distance. While a sword is more difficult to use the it looks, given a little pratice and keeping in mind zombies aren't exactly fighting back, it is an effective weapon....generally. As I can be quoted saying, enviroment is crucial. A sword may be good in well in a open space against one or two zombies, but in a narrow hallway you're going to find it difficult to draw it and gain enough room to get enough momentum to do serious damage.
Zombies are not smart, and knowledge is by far your greatest weapon.
Lure them into traps, play the enviroment to your advantage. Stairs can help you gain distance, as can the ability to climb walls. Keep you eyes peeled, plan ahead, and stay sharp.
Katana as a zombie weapon = shit, they were never meant to cut through a skull. Rather made to cut skin and what not.
For myself, as a close combat weapon, I'd use a 2 foot long crowbar, the reach isn't too great, but light enough to wave around for awhile and can be used to pry things open. Firearms wise, id use my .22 Marlin. Powerful enough to crack through a human skull at a small to moderate distance. If the zeds are far away, why bother shooting? Just take off and that's that. For close distance firearms, I'd use a mossberg 500, nice compact and easy to use. and im also planning on buy spear heads and butt caps so I can make my own spear. That should do nicely =)