GameShark Codes for:

Half-Life

Effect                                   Code

Half-Life

(M) Must Be On                           EC8783A81431D934

Unlock Alien Mode Cheat                  4CA573BA1456F025

Unlock Infinite Ammo Cheat               4CA573721456F025

Unlock Invincibility Cheat               4CA5735A1456F025

Unlock Invisibility Cheat                4CA5738A1456F025

Unlock Slow Motion Cheat                 4CA573A21456F025

Unlock Xen Gravity Cheat                 4CA573421456F025