I just got the Katana body on Halo 3 by glitch. I didn't do it on purpose, so I won't get in trouble. But a glitch happened when I got this one Achievement and it gave me the Katana body, Security Helmet, and Rogue Helmet.

I dunno. I hear that the next Achievement I get will take it away until I get it the right way, but I'm enjoying it while it lasts! :D