- Master Code – Must Be On
EC8783A8 1431D934 - Unlock Alien Mode
4CA573BA 1456F025 - Unlock Infinite Ammo
4CA57372 1456F025 - Unlock Invincibility
4CA5735A 1456F025 - Unlock Invisibility
4CA5738A 1456F025 - Unlock Slow Motion
4CA573A2 1456F025 - Unlock Xen Gravity
4CA57342 1456F025
Half-Life - GameShark Codes
The following are known GameShark Codes for Half-Life on Sony Playstation 2 (PS2).