You can play invincibly, but you have to beat the game on normal mode -and- you have to beat all of the challenges of the gods and unlock the combat arena. In the combat arena, select infinite health, magic and special, select a gaggle of gorgons and die by jumping while stoned repeatedly until the game asks you if you want to play in easy mode. Choose no, and load a new game. Your new game will enable you infinite health, and all your weapons will be available and maxed out. Be careful though, using the cestus to break things that you shouldn't be able to break yet will ruin your game. (This is a really easy way to earn the platinum trophy's hardest gold trophies: aMAZEd, and beating titan mode. Select "titan mode" when you are in the combat arena and you will have invincibility during your playthrough of the titan mode game.)
the nearest you can get to it without hacking is to put it on easy otherwise there isn't any codes or buttons
there is none, but their is a health cheat and an armor cheat.
No there is not
infinity heath
You would need to edit game options and on shields and health put invulnerable.
nowhere because there are no cheat codes for halo 3
There isn't a known cheat code for this on Halo 3.
NO
there is no codes in halo 3 ... -.-
yes
NO
I'm sorry, whoever told you that there was a Halo 3 cheat has lied.(Yes there are glitches, but absolutely nocheats)