The following are known GameShark Codes for Half-Life on Sony Playstation 2 (PS2).

• 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