Depends on your definition of cool. It is an opinion.
All the armor are the same it's just the way how you want to look WRONG! the best armor in halo 3 is the recon armor and you have to be a member of bungie OR get all 7 vidmasters in halo 3 ODST
you have to get 49+ acheivments
you have to get 49+ acheivments
To get security armor in Halo 3... all you have to do is get all of the original 49 achievements (you don't need the new mythic or legendary achievements).
you have to get 49+ acheivments
Security ArmorSecurity Shoulder ArmorYou unlock the Security Armor in Halo 3 by completing the achievements. To get the Shoulder Armor, you will need to get 700-850 GamerScore.NOTE: Sometimes the game glitches and the player is unable to get the Security armor.
Please be more specific next time. If you mean halo 3 mission, the coolest would be the last one, Halo, because everyone is blowing up. If you mean "Is halo 3 the coolest Halo game?" no, Halo Reach is.
Depends on your definition of cool. It is an opinion.
http://hubpages.com/hub/Halo-3-Armor
No, there is no armor in Halo 3 that has a knife in the shoulder.
Technically no, the only way to wear armor in halo 3 that you can wear in reach is some of the basic armor that was already available but the new pieces of armor such as the security shoulders, sapper chest with robot arm, an gungir helmet are only available in Reach.
Yes, there is a Security armor in Halo 3, Only the head and shoulders are unlockable.To get the head, you need the gamerscore in Halo 3 to be 1000g/1000g. And for the shoulders, the gamerscore is variable from 700-800 for some reason. (Note: If you get the shoulders, there is a glitch that makes you lose them when you earn them, but don't worry, they return back.)I hope this is useful!