This will replace the Nuke pack 4 nuke sound to the one from World in Conflict, personally I couldn't stand the nuke sound from the pack so I changed it, but you may prefer the original. If you do download this replacement, I recommend you make a backup of the file being replaced if you want to change it back.
Since it's a replacement you will require the Nuke pack 4
http://www.garrysmod.org/downloads/?a=view&id=40859