No. There is no cheats or glitches to unlock anything in Halo 3. You cannot gamesave on Halo 3 either.
Although there are no IN game glitches to unlock armor, you can use certain downloadable programs that can unlock the achievements for your gamertag which will inturn unlock the armour., however these are detected almost instantly and will result in a ban from Xbox Live.
Many sites claim to have the ability to unlock all the armours, including the elusive Recon and Bungie armour, however such sites are scams and will simply steal your gamertag and/or email account. The only people with the power to unlock those armours are Bungie, the creators of Halo 3.
Update: You can now also unlock Recon armour by earning (Or using the method I mentioned earlier) to get all the "Vidmaster" achievements over Halo 3 and Halo 3: ODST. You then go onto the Bungie website and you can unlock the armour for use ingame.
There isn't a known cheat code for this on Halo 3.
no just work for the armor
there is no permanent cheats in halo 3. you need to unlock them by achievments. and, you can not get the flaming armor effect, it is only for bungie employees. in halo reach, buy the legendary package to get that armor effect.
NO
You unlock the armor.
No.
go to http://hubpages.com/hub/Halo-3-Armor
You unlock the odst armor by unlocking the UNSC SPARTAN achievement
No. Bungie's gives you the armor as an award. You can't cheat the armor, unless you can cheat them.
you have to get 49+ acheivments
nope but you can hack or if you have a friend who works at Bungie he could give it to you. Also, you can now get Recon armor by completing all of the Vidmaster challenges in Halo 3 and Halo 3: ODST and then going to Bungie.net to unlock it.
you have to complete halo 3 odst on legendary, have xbox live and complete halo 3 on legendary