I've noticed a bit of a trend here and I'm kind of upset no one has really addressed it. This is almost exclusively directed towards those who are claiming they would not use a gun.
1) "I'd use a katana/machete/knife/dive down a zombies throat"
You watched your mother die. Your father is missing. You're alone and scared and all you have is that flimsy display sword you bought at the flee market from a Chinese man that claimed it was used by a real soldier, even though "Made in China" is stamped directly on the blade. You hear a noise, then a groan. You clutch your toy sword tightly in your sweating palms and feel the pretty polyester wrap begin to shift. There's another noise, closer this time and you can smell the putrid breath as another groans crawls out of the monsters throat. You try to get away, but it see you. It'd face it half eaten and it's skin pale, almost blue in color. The clothing that hangs off it's bloody, decaying frame is hardly ribbons and the beast comes shambling towards you, mouth open and arms outstretched. You're going to kill that with your sword? The one you had to sharpen with a grinder in the garage because you don't know where to buy a whetstone?
I understand the idea behind melee weapons. They're quiet. But efficient? Are they really your best bet? Ideally, during a zombie outbreak you'll never see a single walker, let alone be within arms reach. How many of you suggesting katana and machetes have any real experience with a sword and the two months you spent doing kendo at the local dojo before you couldn't afford lessons and had to quit don't count. How many of you have any actual experience? Furthermore, how many of you have ever been in a combat situation? A kill or be killed moment where you managed to prevail?
As far as I'm concerned, anyone who honestly and whole heartedly believes they would use a melee weapon on a zombie in a real life situation is lying to themselves and anyone stupid enough to even attempt going High School of the Dead on a small group is only contributing to the zombie problem.
Have you ever consider blood and jibs? You get a bit of blood in your mouth or eye, hell, if it's on your skin too long you are likely to become infected. What do you plan to wear when you go on your zombicidal mission to get yourself eaten?
Goggles? Good job obstructing your peripheral vision, essential to the situational awareness you're going to need to not get stuck up on. Glasses? Because nothing is going to get around those. What about your arms and hands? Gloves? They better fit well, or the grip on your weapon will be compromised.
Melee might be a useful way to quietly dispatch lone zombies, but it is really the quietest or most efficient?
2) I'd use a crossbow!
Understandable, I suppose. In the right situation, perhaps even a viable strategy. If you have a couple of people all with crossbows, you would be able to silently eliminate the undead in small groups. But what are some things you will need to consider?
I had a plastic bow when I was younger. 30-40 lbs draw, if I remember correctly. I was supposed to keep it unstrung at all times, unless I was using it. How long, exactly, does a crossbow last before it loses its tension? How long before the strings need to be replaced or the flex in the arms is all but there? This is a question, because I don't honestly know, but it is something that I think may need to be considered. The main argument made against guns can be made against crossbows aswell.
Crossbows require ammunition. You won't have unlimited arrows/bolts/whatever. What will you do when you run out? Make more? Do you honestly believe you are capable of crafting an arrow that will fly true? Sure, you very well may be able to. However, you can also repack spent shells.
You might also want to consider maintenance. What's easier to maintain, a gun or a crossbow? Again, I'm just posing this as a question. I'm not claiming which would be easier, if either.
Compared to fire arms, crossbows have less penetration, a slow rate of fire and I would say would require a much high level of skill to skillfully operate at longer ranges. Most guns are cut an clear. Point, shoot. You don't have to worry a whole lot about bullet drop, because I don't think many people would be popping off shots at very long ranges anyway. As far as I'm concerned, any firearm is vastly superior to a crossbow, especially when it comes to human verse human scenarios which will likely be more common and more deadly than zombies anyway.
If ever zombies do become a real threat, people who want to go running in with swords and axes are going to be the first to die. When dealing with zombies, you want to stay as far away as possible and avoid them at all costs. That means not smashing them with a baseball bat or hacking them up with a katana. . . rather, trying to. Guns keep you at a safe distance. Gun protect you a lot more effectively against other survivors. Guns, quite simply, are the answer. It's just a matter of which one.
Now, don't take this the wrong way. I know some people are going to be all sour over this. It may be handy to keep a melee weapon on hand, but that doesn't mean you disregard firearms entirely. Hell, you can make your gun your melee weapon. That's just my two cents. Carry on.
Remington RSASS, also please come up with something other than AK-47, be original
Why should we be original? OP wasn't asking for the weirdest gun you'd want to survive with, or the rarest or the coolest. An AK47 is a solid answer and many points have been brought up to support it. This is a question of survival, not creativity.