I have bolded the ones you must get if you want to live:
Sniper Rifle, DB Shotgun, Butterfly Knife, Shotgun (Ephi's), Old School Rifle, Assault Rifle, Combat Rifle, Dead Ringer, Revolver, Frag Grenade, Laser Carbine, Beam Rifle, Alien Blaster, Landmine, Switch Blade, Fist, Pill...
I am thinking of more.