In Halo 3, you need 1000 GamerPoints to get the Katana, does it matter...

[someone]

...which achievements you do to get them? or do you need to do ALL of them.. now that there are more than 49...

 

[J-Dog]

There has been a glitch where people lose or aren't unlocking their katana, or they are getting it early, but you should only have to unlock the 49 original achievements.

 

[HK18]

you need to get the original ones