M6D Pistol: A small, slow-firing human pistol. When used in the game it has a long-range "scope" effect suitable for sniping. A pistol magazine is 12 shots; you can carry up to 20 spares (a total of 252 rounds).
MA5B Assault Rifle: This machine gun has a variable rate of fire, which is controlled by the Xbox's pressure-sensitive buttons. It has a built-in ammo usage display, as well as a rudimentary compass (it shows the direction to the gas giant Threshhold). A magazine holds 60 shots, and you can carry 10 spares - a total of 660 rounds.
M19 SSM Rocket Launcher: This rocket launcher is designed to take out large, hardened targets like bunkers or big tanks. It has two barrels, and can fire two rockets in rapid succession before it must be reloaded. This behavior is suspiciously similar to that of the rocket launcher from Marathon. It has a 2x zoom available. You can hold a maximum of 6 spare rocket packs (a total of 14 rockets, counting the loaded 2).
S2 AM Sniper Rifle: This high-powered rifle can zoom in on its target, with a blurry depth-of-field effect. It is capable of penetrating "thirteen feet of meat and bone", according to the Halo Updates. It has a 2x and 10x zoom, and a night vision mode. There are 4 rounds per magazine, and you can carry 6 spare magazines (30 shots total).
M90 Shotgun: The shotgun was originally equipped with a built-in flashlight, but now that flashlight is built into the Cyborg's armor.
Grenade: Handheld explosives. There are two types of grenade: Human fragmentation grenades, which explode, and Covenant plasma grenades, which emit a glowing blue blast and have a nasty way of sticking to targets.
Fuel Rod Gun: This gun fires powerful bolts of plasma, which explode on impact. It is used by Hunters, the Banshee, and, later in the game, the Grunts.
Plasma Rifle: Like the pistol, this gun can overheat in use, and cannot be recharged. Unlike the pistol, it is automatic, and holds 100 shots. It has no overcharge mode.
Plasma Pistol: This weapon fires a stream of energy bolts, and can also be "overcharged" to produce a much larger blast. It is not automatic, and can overheat (requiring a cooldown period). It cannot be recharged, but it holds about 100 small shots or 8 fully charged bolts.
Needler: This nasty weapon shoots a rapid stream of small darts or needles, which stick into a target and explode a few seconds after impact. Needles can track their target.