GTA Ammunition 25% discount: Go to the back of the Ammunition weapon shop and complete all of the range challenges with Gold. You’ll receive a lifetime 25 percent off discount in the entire store.
GTA Free weapon upgrades: Died by blowing yourself up with a grenade after buying any weapon upgrades at Ammunition? The cash you had before you bought the upgrades will be returned to you once you re-spawn. You’ll also still have the weapon upgrades in your possession, essentially giving yourself free weapon upgrades.
GTA Earn the Out of Your Depth Achievement/Trophy: Grab a boat or jet ski and head out to the deep ocean until the water changes to a dark blue hue. Before long, a red icon should show up on your map. The red icon means that a shark is nearby. From here, just jump into the water and wait for the shark to kill you. This will grant you the Out of Your Depth achievement/trophy.
For the entire list of cheats, visit http://www.gta5cheats.com