If you meant to become invincible, there is a piece of equipment you can pick up in Campaign called Invincibility. It's dropped by Brute Chieftains and renders the user invincible for 12 seconds.
The other way to become invincible is edit the settings in Forge or Custom Games. You can set your level of health, your recharge rate, your level of shielding, your ammo, your movement, and your damage. For health, damage, and ammo, you can set all of those to infinite if you so please.
No you can not. There is no "God Mode" in Halo 2.
Um...if you mean "is there a theatre mode in halo 3," then yes.
yes
You mess up all your bad guns
Yes, there will be Forge mode in Halo 3: ODST... but on the other hand there is two discs so there might not be in the halo ODST disc.:)
yes
Yes you can have up to four people in story mode.
yes fire fight mode is addicting! somwhat dissapointing
haw to make mode maps in halo 3
Forge mode
in sandbox mode
All you have to do to view (or record) your clips in Halo 3 is to go to Theater mode.
Sandtrap.