Well I decided to tell everybody something that I wasnt going to but now I am.
Some people might have known it but didnt say anything.

On the old nazi zombie map the entire wall that has the ammo box and tile glitches on it is glitched!

You can run and jump from anywhere to any spot on the wall and its a glitch.
The backside of the wall does not work but the 2 ends and any of the entire front part will work.

Also the little piece of wall sticking out inbetween a window and a doorway near that wall I was talking about is also glitched.
Run and jump into the front of it and you have yourself another glitch.
On this one the zombies from the window and doorway can get you but the ones from the front cannot.

This way of glitching will easily get you to whatever level you wanted to get to because if one way doesnt work for you then you can just try a different way.

!!!REMEMBER!!!
The further you jump from into any glitch the further the zombies will stay.