You need to unlock the weapons.
i believe there are 15 prestige levels in call of duty black ops.once compeleted 15th prestige you will unlock gold camo for all of your weapons.
The Call of Duty Wikia has a complete list of the Call of Duty Black Ops weapons from the related link
you can't actually hack into it. you just have to level up all they and unlock as you go, sorry
an achievement
Just kill people
its one of the first things u unlock
Ranking up...
You get to 14th prestige
doa zork 3arc unlock
you can get it at campaign or unlock it on multiplayer
level up
HK21 upgraded with a reflex sight