GTA 5 god mode: PAINKILLER
PAINKILLER (phone 1-999-7246545537) makes you invincible for 5 minutes. There's no permanent god mode in Story Mode: when it runs out, just enter it again.
Pair it with TURTLE to refill health and armor instantly, and LAWYERUP to drop your wanted level one star at a time.
How to enter a GTA 5 cheat
PC: in Story Mode press ~ (left of 1), type the code and press Enter. PS and Xbox (and PC): open the in-game phone, go to Contacts → Keypad and dial the 1-999 number. Cheats don't work in GTA Online and switch off achievements and trophies until you reload a save.