God Mode Hacks for World of Warcraft are designed to make your character undefeatable. You'll see a number of guides online that purport to show you how to implement this hack. There's only one little catch. They only work on private servers and they only work if the guy who runs the private server likes you and deems you worthy of God mode. Somehow they fail to mention this when they show off how awesome God Mode is.
Now maybe you think the idea of playing on a private server instead of Blizzard's servers is awesome, but personally I can't deal with the high latency or having to suck up to server owners. Ugh. At any rate, save your money on the God Mode hack if you only ever play on Blizzard servers because you're just throwing your money away.