In the very first arrival mission at Nui Pek as soon as you exit the chopper go right to the entrance of your bunk before talking to the captain or anyone else Try opening the locked door ten times On the tenth attempt you will hear laughter Keep trying and on the 13th attempt you will get the M79 grenade launcher keep trying and on the 15th try some scary music will play and a VC zombie will walk at you with his arms straight out and his eyes rolling in his head You can now either shoot him or enter the jeep and drive around camp