Tactical Insertion

In-Game
Tactical Insertion is an equipment item usable in Modern Warfare 2's multiplayer. In-game, Tactical Insertion takes the form of a flare which is dropped where ever the player wishes to be respawned. It disappears upon respawn, so if a player wishes to continue spawning in the same spot he must deploy another.

Players have been known to wait by Tactical Insertion flares, hoping for a relatively easy spawn kill. 25 spawn kills from an enemy Tactical Insertion flare awards the "Tactical Deletion" (abbreviated TacDel) challenge and callsign title. Furthermore, SitRep makes Tactical Insertions show up red from any point in the map, even through walls. Tactical Insertion is unlocked at level 11. It is important to note that it takes about 3 seconds to light and drop the flare. During this time the user is defenceless against any attackers, but can cancel preping the flare and switch back to their weapon. Tactical Insertion users can pick their flares back up to place them somewhere else if they so desire. Tactical Insertion flares can be destroyed by gunfire or manually.

Killing an enemy within five seconds of tactically inserting five times completes the challenge Jack-In-The-Box I, unlocking the title by the same name. Jack-In-The-Box II requires 25 kills within five seconds of insertion and unlocks the Ta-Da! title.

Tactics
It's generally advised to use the Tactical Insertion in any game type in which you may be defending something, provided respawns are enabled. Hiding your Insertion in proximity to an integral flag in Domination is an excellent and widely-used way to make the best of it. Placing your Insertion in a discrete place close to an objective in Demolition (or Sabotage, though there is a respawn delay to be wary of in Sabotage matches) is an excellent way to prevent bombs from being planted or defused. Taking a moment before grabbing the enemy's flag in Capture the Flag can be useful as well, though not as much because of respawn delay. Tactical Insertions also have a use in Team Deathmatch games if you are trying to hold down a camping spot that may be hard to get to, but this is generally not advised as you may respawn directly into your killer's line of fire if he sees or hears the flare. Beware the glow of the flare itself as it will shine through walls, projecting a red glow on the other side if left too close. The best way to hide a flare is to put it in a place the enemy cannot easily get to or damage. A good example would be in the bathroom's in the house in the map, Estate and the crane and building ledges on Highrise. Both these points are not easy to reach and become relatively easy to score easy kills with repeated spawns. These are also very useful while calling in Care Packages, Sentry guns and Emergency Airdrops as it allows you to respawn next to it should you be killed. A more unorthodox method of changing a loadout, is dropping the flare, killing yourself, and respawning on top of the TI. Sure, it costs you a life, but hey, you got your class!

The main thing you want to avoid is using Tactical Insertion in a Deathmatch right near someone. If they kill you, they'll kill you again when you respawn, granting that player/team more points.

A less common use is to drop a Tactical Insertion while defending a point in Headquarters. It won't help you defend, but once the enemy destroys the headquarters you may get the drop on a cluster of unsuspecting enemies.

Trivia

 * Friendly Tactical Insertions are green with the teams symbol, while enemy flares are red.
 * If the Tactical Insertion is stopped by switching weapons, the sound of the flare being prepped can be heard even when the other weapon is drawn, even though the flare is not dropped.
 * Tactical Insertions can be destroyed by gunshot, knife, killstreaks, falling airdrops, or if a player walks up to it and presses the action button.
 * Many glitchers use this, so they can spawn back into a glitch if they die, or at a point in a glitch which is hard to reach. They are also used by glitchers to achieve easy killstreak rewards such as the care package or emergency airdrop to utilize for glitching.
 * Tactical Insertions are also used by Nuke Boosters, allowing them to save time in finding the friend that they are boosting with. Counter Nuke boosters often use SitRep to track down their tactical insertions.
 * The Tactical Insertion can be concealed from enemies by deploying it in something with a red glow, like the heater in Derail.
 * The Tactical Insertion doesn't work in Search & Destroy, because you can't respawn after dying, although you can use it as a trap.
 * It's a good piece of equipment because it can be thrown in the HQ matches on the HQ so if you are killed you respawn in the HQ to keep capturing. But obviously the enemy doesn't have to detect it and destroy it, or, if you capture the base you can put a TI by it. Once you die and the other team takes the HQ, you can rush in and kill them all.
 * It is remarkably underused as it has to be redeployed after every use and it takes time to prep.
 * It is however useful to an extent in Search and Destroy, against inexperienced players mainly. If the player is defending the targets, they could place a TI at one target, and guard the other one. If an enemy player destroys the TI, then it will alert the player who placed it, so they will know where they are.
 * Tactical Insertion flares are very fragile and are easily destroyed by stray gunfire and grenades, so be sure to place them in an area where they aren't likely to be a victim of collateral damage.
 * Tactical Insertions are actually just regular Flares.
 * The flare that you fire at the end of the mission Whiskey Hotel is a complete reuse of the Tactical Insertion model and skin.
 * Having the Martyrdom Deathstreak with a Tactical Insertion is not advised. The Grenade could destroy your flare, or even worse, kill you when respawning.
 * If you kill an enemy within a few seconds of deploying a Tactical Insertion, your enemy will see you deploy it on killcam. It's best to wait a moment, or move the T.I. after a kill so your T.I. doesn't get smashed, or worse, you get spawn-killed.