Ordnance pod

Resupply canisters, or ordnance pods, are rearmament capsules frequently used to rearm UNSC ground units in hazardous combat situations.

Description
A resupply canister is a long, oblong capsule painted in olive green drab. In the interior is a stiff blue or black/gray foam that encapsulates a firearm, typically an M7 submachine gun, BR55 battle rifle, M90 shotgun, SRS99C-S2 AM sniper rifle, MA5C assault rifle, or M41 rocket launcher. Upon impact, panels on the upper surfaces of the capsule pop off, revealing a partial profile of the weapon within. Pelican dropships may carry six resupply canisters on their tail assemblies and eject them in sequence, allowing the capsules to air-drop to the ground and implant themselves firmly into the ground, similar to the ODST Human Entry Vehicle.

Types of resupply canisters
There are at least four types of resupply canisters: The Type-B Capsule, and the Type-C Capsule. The Type-B Capsule, which has a length of 2.76 meters (9.06 feet), was used in Halo 2, and the Type-C Capsule was used in Halo 3. The difference between Type-B's and Type-C's is that Type-B's lack the rounded part on top, the flashing red light, and the pop off protection panel. There is also a more streamlined variant of resupply canister that is commonly dropped by Longswords to deliver ordnance to ground forces.

The fourth type is an ordnance pod, formally designated as the M2859 Materiel Acquisition Pod. Developed by Misriah Armory and commonly employed in the years following the Human-Covenant War, they are often deployed for UNSC forces deep behind enemy lines or outside the range of a forward operating base.

In-game
They also appear by default on the multiplayer level High Ground and on Valhalla, having been dropped by Victor 398 before crash landing. In Forge, players can spawn the pods, but not delete opened ones. If one is spawned couple feet off the ground, the panel comes off but will spawn a full capsule.

Trivia

 * In the Halo 2 level Delta Halo it is possible to move these weapon capsules after they have been deployed by a Pelican by pushing them with a Scorpion or Wraith.
 * These pods can kill the player in Halo 2 if one stands right under them when they are dropped.
 * In Halo: Reach during the start of Firefight matches, a Longsword can be seen dropping ordnance pods that resembles a resupply canister (they usually contain heavy weapons).
 * In Halo 3 via Forge, players can embed them into the ground, creating vehicle barriers.

List of appearances

 * Halo 2
 * Halo 3
 * Halo: Reach
 * Halo 4
 * Spartan Ops