add_zombie_powerup( powerup_name, model_name, hint, fx )

This might do the trick.

EDIT: just as a reference as to how Treyarch does it:

add_zombie_powerup( "double_points","zombie_x2_icon",   &"ZOMBIE_POWERUP_DOUBLE_POINTS" );

cheers dd ill let you know if it works but where do i add that? i know nothing about scripting

do you have the fire sale set up? if so, would it be possible for you to post a tutorial i would really like that powerup in my map

i will post a tut if someone will be willing to script the firesale powerup other wise its useless

Well, did the powerup spawn?

it spawned but did nothing ive asked sparkymcsparks and he said you will have to port the model and take the script from bo1 as firesale wasnt in waw

lol and anyways there is not one tut on how to do a fire sale it all depends on which scriipt placer you used

Well of course it didn't do anything. The function only adds the firesale model to the array to be spawned and doesn't include the affect. I don't know why you'd think otherwise.