Since this is a Solo guide, I'll relate to the Singleplayer difficulty and you'll need a healthy amount of skill for this strategy to be useful.
First of all you go and buy yourself a M14. Sounds weird, but you'll see, we will save a few bucks with that. In the first round you knife everything that is moving. You should end up with around 800 points you can open the bar with. In the second round you shoot the zombies six times in the chest and then knife them to receive as much points as possible. Do this, until your 1911 runs out of ammo. That's where the M14 comes to use. Instead of going to the "Mystery Chest" and risk getting EMP grenades or something like that, you just use the 450 points cheaper and quite effective M14. In the third round you should start to use it, because you need over a whole M1911 magazine and a knife hit to kill a zombie. By following this strategy to the fifth or sixth you should end up with around 6000 points. Most of you can imagine what we'll buy next... The Galvaknuckles! The two big advantages are: It kills zeds with one hit up the 14th round and is much faster than the knife.

After getting the Galvaknuckles you should try knife only. This will get you easily many points. In the time to the 14th round you have to get the 4 perks: Juggernog, Revive, Speed Cola, Double-Tap. You will have these around the 10th round. Now is the time to get a nice gun. Use the Mystery Chest. Here are some good guns(of course every gun should be punched):
-DSR (It gets really effective, when you punch it a few times. After the first time you get the chance to get it with a silencer and a scope and, the version that i prefer, the DSR without a silencer and without a scope. I'll post a pic of it.)
-Executioner (Kills zombies with a one hit pretty long)
-RPD
-HAMR
-Galil
-Raygun
-RPG (To turn walkers into crawlers. Thanks to the commenters.)
Even though you have some nice weapons at this point try to use the Galvaknuckles to the 14th round as often as possible.

What you have to do now is pretty easy. Try making an eight on the map (I'll post a few pics). You don't even need to run, because running zombies are as fast as you walking. While making these eights you have to watch out, to not stand in any corners, because otherwise the zombies will trap you.

You can do this in Co-Op too but then i'd change the "Revive" to "Stamin-Up" and the Balistic Knife is a nice sidearm when punched. Thanks for reading this and bye! :D

Hey guys,
I just wanted to thank every commenter and everyone who rated this guide.
It's crazy how I'm still getting comments, even though I created this ♥♥♥♥ over three years ago.
Stay cool