TR/9 trip mine

The TR/9 Antipersonnel Mine, otherwise known as the Trip Mine or Mine, is a UNSC Equipment item usable only in Halo 3.

Overview
The Trip Mine is activated by proximity, or by impact of a vehicle or personnel. Once deployed, it can be identified by a high-pitched beeping noise, four inner spokes that rise up and a distinctive flashing bright orange light on its top. Its blast radius is considerably larger than a grenade or rocket explosion, throwing vehicles and personnel into the air. The Trip Mine cannot be deactivated once deployed, but it will explode after about ninety seconds if it's not triggered. However, it can be destroyed by any weapon.

There is no device that can remotely detonate the mine. The Trip Mine, while having a larger blast radius than a Frag Grenade, will only slightly injure a Spartan or Elite when they are positioned near the edge of the blast radius. It will, however, kill Brutes and unwary Marines, even if they are on the edge of the blast. The greater damage to Marines and Brutes may be due to the fact that their armor is weaker than the Mark VI and Elite shielding. The fragments will slip through their armor, thus killing them.

It is possible to avoid detonating an activated Trip Mine. Notice that when a player crouches while moving forward, he or she doesn't show up on the motion tracker. So if a player is crouched, that player can safely bypass the trip mines, however, the player should still be aware of the mine time limit.

The Trip Mine spawns by default on Sandtrap, Rat's Nest, and Avalanche. Destroying an enemy vehicle with the trip mine in campaign or multiplayer will unlock the "We're In For Some Chop" achievement. Brutes with jet packs will deploy Trip Mines if you are close by. In multiplayer, a single Trip Mine is incapable of killing a player; it will only injure them. On foot, a player must have two or more Mines available to kill someone with a full shield without the assistance of a weapon or grenade. This is impractical because a player cannot carry multiple Trip Mines, and the player's victim will most likely avoid a second Trip Mine. Vehicles that use anti-gravity ( Ghosts and Wraiths) can also be damaged or destroyed by the mines. A vehicle that doesn't touch the mine, but gets close can cause it to detonate.

Also, in multiplayer maps, Trip Mines can be used as part of a known glitch, commonly called overloading a map, to disable certain parts of a map, such as Gravity lifts, Man Cannons, Sandtrap's minefield, and Snowbound's Automated Turrets/ guardians, as well as Sandbox's Automated Turret/guardians.

Tactics

 * The most important thing to note when deploying a Trip Mine is to inform your allies. Most of the time, they will activate your trap, resulting in you betraying them.
 * When running away from an enemy vehicle, a Trip Mine can be deployed in front of the approaching vehicle. This may kill the occupants of the vehicle but it carries the risk of killing the player who deployed it.
 * Try to combine the powers of the Trip Mine with different pieces of Equipment to make interesting effects. For example, it's useful to drop a trip mine into an enemy Bubble Shield. The resulting blast will be contained within the Bubble Shield, killing your opponent but keeping the player who deployed it from receiving any damage in return (if the player is not within the bubble shield). There's still the possibility of the explosion destroying said bubble shield however, so remain wary.
 * If you deploy a Trip Mine on top of a Man Cannon, the mine will go flying out into the battle field. Throughout the Halo 3 Beta, the Trip Mine would sometimes disappear entirely when thrown into the Man Cannon. It would still explode if someone or something goes within the activation radius.
 * One of the most evil tricks, as Bungie mentioned before, is to deploy a mine in the exact position where it spawns. Some players will notice that the mine is armed (by noticing its distinct audio and visual cues), but most players will attempt to collect it, resulting in a kill (if the player's shield is almost depleted) which would certainly not have happened if the player is attentive. However, this tactic can kill teammates also, so it is wise to communicate with them
 * Place Trip Mines in doorways or Sniper perches, someone will step on it eventually.
 * Throwing a Fragmentation Grenade at a Trip Mine can cause extra damage.
 * If a player walks slow enough or crouch-walks over a Trip Mine, it will not explode. Although you are doomed if any enemy sees you doing this.
 * The Trip Mine's glow and beeping sound gives it away (as mentioned in disadvantages), although, it can be placed on the one side of a hill, as an example, so the driver of a vehicle will still hear it, but not see it as they are passing from the other side. The Trip Mine will detonate when the vehicle passes over the hill.
 * Another tactic is to throw a Trip Mine under a vehicle, so it is harder to see and the sound is muffled. When a player moves while in the vehicle he or she will activate the trip mine. This works especially well on enemy aircraft.
 * In Capture the Flag, a player can place a Trip Mine by their own flag. It will kill any opponents that are trying to steal the flag. This tactic works very well when one flag gets the win. A good deal of players are focusing on getting the flag, so the Trip Mine would be ignored until it detonates.
 * In the level Tsavo Highway, Trip Mines are a useful way of destroying the Brute Choppers by throwing it at the Chopper once it starts charging at you. They are a one-hit-kill on normal difficulties and lower, allowing players to unlock the "We're in for some Chop" achievement. To make this easier, a Plasma Pistol overload can be used to disable the Chopper. When it is stationary, a Trip Mine can be placed right in front of it, guaranteeing death for the enemy.
 * In multiplayer, Banshees are commonly used to splatter enemies. If you happen to see a Banshee angling toward you and boosting, drop a Trip Mine. The explosion will probably kill both of you, but is usually still desirable, as Banshees are often hard to kill.
 * If a player has low shields and an enemy is chasing him/her, a good tactic is to throw the Trip Mine down. So when the enemy comes around the corner, it will explode, taking down his/her shields. He/she can then be finished off with a shot from a Battle Rifle or the Covenant Carbine. If the opponent hears the beeping and doesn't come around the corner, it gives the player chance for his/her shields to recharge.
 * Always remember where you left your Trip Mines and tell your teammates as well to avoid betrayal.
 * If you deploy a Trip Mine on an occupied vehicle, it is possible for it to explode immediately either destroying or disabling the vehicle. But it's most likely to kill you also.
 * A single Trip Mine can kill a player, however it will generally only deplete their shields.
 * It can be thrown straight at a players face at point blank as a sacrifice if your shields are down.
 * Trip Mines can be bounced off overshield power ups.
 * Try making Trip Mines land upside down by bouncing off a wall or solid object, because they are much harder to see, since the light is pointed into the floor/ground.
 * The mine is effective against running brutes and all types of vehicles.
 * A Trip Mine plus a fragmentation grenade is an effective way to take out that annoying bunny-hopping camper. Just throw the Mine, toss a frag, and watch the beautiful fireworks.

Disadvantages

 * Sometimes, while playing in multiplayer or campaign, you can either accidentally run, or drive over your own self-activated Trip Mines or in Co-Op you can obliviously run over your teammate's Trip Mine. Without proper communication, you may also end up killing your own teammates with this device.
 * Be aware about where you are tossing the Trip Mine and don't forget its location.
 * Players can be clever and use their enemy's Trip Mines against them, by luring them into the blast radius.
 * It is easy for an enemy to see a Trip Mine, that you have deployed due to it's glow. Additionally it makes a distinct beeping noise.
 * While it could instantly destroy vehicles in the Beta, it now only takes down shields; however, for whatever reason, most riders in a vehicle will be killed by directly driving over a Trip Mine in the final version of Halo 3, even though their vehicle may suffer only minor damage.
 * In High Ground, the trip mine can be used to barricade the openings in the base, namely the knocked down wall and small hut-like building on the western side outside the base but players on the other side would wait and stay outside of the base until the Trip Mines explodes automatically.
 * The Trip Mine is fairly small, so vehicles could easily evade it but if the vehicle evades it but is close enough, the mine will explode.
 * The Trip Mine will only stay active for 90 seconds, so if you have a place wired with Trip Mines they might go off before another player steps close to one.
 * If shot, the trip mine will explode, which makes it easy to avoid if you shoot it from a far enough range.
 * The Trip Mine is often difficult to use in split-screen local games due to the sound it makes when deployed, alerting the other players to "screen peek".
 * As depicted in the Halo 3 weapon overview from Machinima's very own SoDaGod, the Tripmine is like a "ninja with foglights in his pockets". This is because the Trip Mine can be heard before seen, or vice versa.

Trivia

 * In multiplayer, sometimes it is referred to as an 'explosive pie' due to a resemblance of a pie from afar and that it is explosive.
 * In Halo 3 Campaign, a Trip Mine can remove Invincibility from a Brute Chieftain wielding a Gravity Hammer.
 * Even though it's said that this is UNSC equipment, the Brutes with jet packs always have one ready to use and no UNSC Marine/ ODST has been seen holding one, though there are several Mines in a Marine base on Tsavo Highway.
 * It was hypothesized that the Trip Mine may be the book-aforementioned Lotus Anti Tank Mine or they may be both made by the same manufacturer. However, it is unlikely the Trip Mine is the Lotus Anti-Tank Mine because a Scorpion Tank can easily drive over a Trip Mine and survive the explosion. It is possible that the Trip Mine is the Antlion Anti-Personnel Mine due to its similar operation.
 * The Trip Mine logo, along with the Bubble Shield logo is a Halo 3 Multiplayer emblem.
 * Trip Mines can be used to overload a map, deactivating certain parts of the map, such as the Automated Plasma Turrets in Snowbound, the Brute Landmines in Sandtrap, or the giant lifts in Blackout, Guardian, and Construct. To overload, you must place a great deal of trip mines through use of a glitch. Keep placing the Trip Mine on one spot until it explodes to do the glitch.
 * During the initial unveiling of Halo 3, a Bungie employee claimed that, "The Trip Mine is probably going to be used as a 'I got you' weapon as people only seem to drop it right before being splattered".
 * It's nearly impossible to kill Jackals with a Trip Mine because Jackals fight and move in crouching positions.
 * You can throw a Mine down on an opponent and follow with a grenade or a headshot for a guaranteed kill with normal shields.
 * In the Halo 3 Beta, deployed Trip Mines could stick to the bottom of a motionless vehicle. If the vehicle then moves, the Trip Mine explodes, killing all players inside with normal shields.
 * It is possible to traverse a Trip Mine if one crouch walks over the top. Note however, that this only works if you are moving slow enough as to not appear on radar.
 * It was described as a "Ninja with fog lights in his pockets" and the fact that you had to hide it, or people would see it by SoDaGod in his description of Halo 3 Equipment on the web series Inside Halo.
 * The Trip Mine is a great way to kill Covenant troops because they are always moving around. Try to throw them into large groups.
 * If you set it off, while looking down at it you will see your body split in half for a moment.
 * By making instant-respawn Trip Mines in Forge and then repeatedly throwing them in a pile, when they explode they will generate enormous explosions that are capable of flipping an Elephant or even crashing the game completely.
 * When overloading a map with Trip Mines it is not uncommon for items (especially vehicles) to disappear and reappear. Items will also commonly randomly spawn for no apparent reason.
 * The shape of the Trip Mine resembles the German made Tellermine series of anti-tank mines developed and used during the Second World War; both mines are hand carried to their targets and are sometimes tossed into the way of an enemy tank in hopes of destroying it.
 * In an interview, a Bungie employee stated that "If you were to turn around and see a warthog driving at you, all you have to do is set the trip mine. Sure, you die, but at least you got those damn bastards who ran you over."