This isn' t really a cheat but it get your levels up really well. At the end of the main quest (amulet of kings) you will have to take martin to the temple of the one, but before you do lord Dagon arrives. When this happens go back to martin and tell him to wait where he is then go back through the gate and there you will find unlimited daedra creatures coming out of oblivion gates,and if you want to last for ages take good health potions in, Good luck.

Skills you get up:

Blade
Blunt
Block
Marksman
Destruction (other magic aswell)
Hand to Hand.