Here is the currently available weapons in halo 4:
UNSC:
Magnum m6h
BR
Dmr
AR
Spartan laser
Rocket launcher
Sniper rifle
M45 shotgun
Remote detenator(rocket pistol)
Frag grenade
Rail gun arc-920
M247h heavy machine gun
Covenant:
T55 storm rifle
T51 covenant carbine
T1 energy sword
T33 needler
T25 plasma pistol
T1 plasma grenade
Plasma turret
Assault carbine
Forerunner:
Z180 scattershot
Light rifle