How to unlock halo 3 Katana and Security Helmet?

[Bobby Flay (NJN 18-19)]

alright, i have 1185 gamer-score for halo 3 i have all the vidmasters, and the new achievements, in total i have 52 achievements. the ones i don't have are... 2 for 1, overkill, killing frenzy,steppin razor, orpheus, and reclaimer. what do i need to do??

 

[wiiman1103]

Get the original acheivments. So do all the ones you just said.