In Halo 4, there are several different options for starting weapons for your different loadouts.
These are all of the starting weapons you can unlock for use in Multiplayer. Any other weapons will be accessible on the map.
Now to get some guns, and kill some frackin aliens!
Primary Weapons
Assault Rifle – Unlocked by default
DMR – Unlocked at rank SR-1
Battle Rifle – Unlocked at rank SR-2 (costs 1 SP)
Covenant Carbine – Unlocked at rank SR-5 (costs 2 SP)
Storm Rifle – Unlocked at rank SR-5 (costs 2 SP)
Light Rifle – Unlocked at rank SR-22 (costs 2 SP)
Suppressor – Unlocked at rank SR-22 (costs 2 SP)
Secondary Weapons
Magnum – Unlocked by default
Plasma Pistol – Unlocked at rank SR-8 (costs 2 SP)
Boltshot – Unlocked at rank SR-18 (costs 2 SP)
Grenades
Frag Grenades – Unlocked by default
Plasma Grenades – Unlocked at rank SR-8 (costs 2 SP)
Pulse Grenades – Unlocked at rank SR-18 (costs 2 SP)