Do you mean that you have to press a button on keyboard or a hud?
Both are able to make, but pressing a button on keyboard is very simple. Here is a script for it:
;Artificial Intelligence Script
;Header
desc = Press ENTER To Pickup Weapon
;Triggers
:state=0:hudreset,hudx=50,hudy=90,hudimagefine=gamecore\text\pressentertouse.tga,hudname=enterhit,hudhide=1,hudmake=display
:state=0:hudreset,hudx=50,hudy=90,hudimagefine=gamecore\text\pickedupaweapon.tga,hudname=weaponprompt,hudhide=1,hudmake=display,state=10
:state=10,plrdistwithin=40,plrusingaction=1:state=1,playertake,coloff,rundecal=-1,plrsound=audiobank\items\pickupweapon.wav,hudshow=weaponprompt,hudfadeout=weaponprompt
:state=10,plrdistwithin=40:hudshow=enterhit,hudfadeout=enterhit
;state=2:state=3,playerdrop,colon,plrsound=audiobank\items\pickup.wav
:state=3,plrdistfurther=65:state=10
;End of Script
So I just added few things to the default weapon.fpi
Thanks,
TP