The following list tells you which level rank in Grand Theft Auto Online you need to be to unlock the weapon listed.

Guns

Rank 1

• Combat Shotgun
• Pistol

Rank 2

• Pistol Clips

Rank 4

• Pistol Flashlight

Rank 5

• Pistol Suppressor
• Micro SMG

Rank 9

• Combat Pistol
• Combat Pistol Extended Clip

Rank 11

• Combat Pistol Suppressor
• SMG

Rank 15

• SMG Supressor
• Rank 17
• Pump Shotgun

Rank 21

• Sniper

Rank 24

• Assault Rifle

Rank 29

• Assault SMG

Rank 33

• AP Pistol

Rank 37

• Assault Shotgun

Rank 42

• Carbine Rifle

Rank 50

• MG

Rank 70

• Advanced Rifle

Rank 80

• Combat MG

Rank 90

• Heavy Sniper

RPG, Grenades, Minigun and Others

Rank 13

• Tear Gas

Rank 15

• Grenades

Rank 19

• Sticky Bomb

Rank 20

• Jerry Can (gasoline)

Rank 60

• Grenade Launcher

Rank 100

• RPG

Rank 120

• Minigun

Personal Armor

Rank 5

• Super Light Armor

Rank 10

• Light Armor

Rank 15

• Standard Armor

Rank 20

• Heavy Armor

Rank 25

• Super Heavy Armor

Auto Armor

Rank 10

• Auto Armor 20%

Rank 30

• Auto Armor 40%

Rank 50

• Auto Armor 60%

Rank 80

• Auto Armor 80%

Rank 100

• Auto Armor 100%