Game Trainers
Game trainers are a type of software that modifies the game code to give the player an advantage over other players. They are often used to cheat, giving the player infinite health, ammunition, or money.
Popular Trainers

Kiddion's Modest Menu
One of the best free mod menus for Grand Theft Auto V.

BakkesMod
The one and only Rocket League trainer with a ton of features.

Impulse Menu
One of the first mod menu trainers for GTA 5.

Menyoo
The most popular GTA 5 mod menu ever released.