Equipment

Halo: Combat Evolved
There were two types of equipment in Halo: Combat Evolved, active camouflage and overshield. Active camouflage made you partially invisible to other players or enemies unless you were shot, which caused your shields to flare, making you visible momentarily. The overshield simply made your shield three times as strong. However, in multiplayer, it slowly went down over time without being shot.

Halo 2
In Halo 2, the only available equipment was Master Chief's flashlight and The Arbiter's active camouflage (Though with a certain skull, Master Chief would gain camouflage as well). Although such equipment could not be collected or spent, they were always available for use (based on charge) being integrated into their respective armor.

Halo 3
In Halo 3, equipment items can be used by Human players and AI units in both Multiplayer and Campaign, though the flashlight remains campaign exclusive. They are placed throughout Campaign levels and Multiplayer maps to add a new strategic (and sometimes humorous) option to the Halo gameplay mix. While most of the equipment is Covenant manufactured, some is Human made, such as the Lotus Anti-Tank Mine (Trip Mine). Others, such as the Auto Turret, are made by the Forerunners. While only one piece of Equipment can be carried at a time, they are usually worth their weight.

In Halo: Combat Evolved
Campaign and Multiplayer: Campaign Only
 * Active Camouflage
 * Overshield
 * Flashlight

In Halo 2
Campaign Only:
 * Flashlight

Multiplayer:
 * Overshield
 * Active Camouflage

In Halo 3
Available in Campaign and Multiplayer:
 * Bubble Shield
 * Power Drain
 * Gravity Lift
 * Trip Mine
 * Regenerator
 * Active Camouflage
 * Overshield
 * Flare
 * Deployable Cover
 * Radar Jammer
 * MJOLNIR Powered Assault Armor (Integrated into armor)
 * Sangheili Personal Energy Shield (Integrated into armor)

Campaign Only:
 * Automated Turret
 * Cloaking
 * Invincibility

Custom Maps Only:
 * Custom Powerup

Trivia

 * In the January 2008 issue of EGM, in an interview with Brian Jarrard and Tyson Green, it was revealed that there was a piece of equipment cut from the final game known as The Vortex. It was said to be deployed the same as a Power Drain, but would instead create a mini black hole that would "suck" in any object within range, and diverting its course into the black hole, and away from your face. It was even able to affect nearby objects such as the Fusion Coil and even other players. The design was cut due to the fact that it was too "expensive" from a networking and performance standpoint.
 * The Radar Jammer, Flare, and Deployable Cover are no longer usable in Matchmaking, as all three could be used to reach unfairly high places; the former two using the Equipment Jumping glitch, and the latter by simply jumping on it after deployment.
 * In the new 2009 Halo 3 Action Figures wave, there are equipments included, and it should be noted that they all can be moved in some way as if they were activated; for example, the Radar Jammer included with the Olive Security-permutation
 * Despite not being able to use them yourself, In Halo 3: ODST, Brutes will use Power Drainers and Flares against you.

Glitches

 * The Radar Jammer, Flare, and Power Drain can all be used to "double jump".
 * In Forge, players often set equipment items to Instant Respawn, resulting in various interesting effects. Among other things, Instant Respawn Trip Mines can be used to overload a map.
 * By putting a trip mine to instant reload, players can overload the map by throwing the trip mine multiple times in succession. Overloading makes some forged objects disappear and disables all stage elements such as lifts and guardian turrets.