Flare

Overview
The flare equipment type is similar in appearance to the Radar Jammer and Power Drain and makes its debut in Halo 3. It functions in a similar manner to a flashbang grenade, blinding foes and allies alike. Its symbol in the HUD is a circle with multiple rays coming from it. This equipment type was only featured in two multiplayer maps by default, including Guardian and Isolation. Both have been removed by an update. It is mainly used to suprise your opponets. However, a planned strategy and a close range weapon or a type of one-shot kill weapon can be used to almost certainly dispatch an enemy in conjunction with a flare. Without a very effective weapon, it is just a nuisance, hindering you just as much as your opponent.

(In reference to the Flare Equipment by Griesmer): The Flare merely creates a blinding white light rather than hurts, anyone friend or foe alike who sees it-and that's OK. "If you have a short range weapon, the flare will blind foes long enough for you to get close" says Griesemer. His favorite strategy? "See a bunch of people guarding the flag? Throw the flare down." He says "By the time the Flare's gone, their flag is too." Just take care to divert your own eyes-the Flare will blind the player who throws it, too. - EGM September 2007 Issue

Disadvantages
The player cannot see the battlefield even if he/she deploys it. There is a way to counter it, but it's difficult. The flare will blind you, but your HUD, and more importantly, your reticule, is unaffected by it. If you're blinded, swing your view around until it turns red, and open fire. Many players have stated getting "lucky kills" by noticing and taking advantage of this.

The other easy way of avoiding being blinded by your own flares is to throw it towards an enemy and then quickly turn around before it goes off. This will damage your vision slightly but won't completely blind you. The same thing works with enemy flares: if you look away as soon as the enemy throws it, then it will only have a weakened effect, and you can still see well enough to shoot your opponents into oblivion while they remain oblivious to your location.

Of course, such strategies will only work on those who are unfamiliar with the tactics discussed here.

Trivia

 * The Flare shares many physical similarities with the Radar Jammer and Power Drain, with exception of a yellow glow instead of a red or blue glow.
 * Although the Flare blinds you completely, it does not get rid of your motion sensor, allowing you to still know where you and your enemies are.
 * One of the best tactics for capture the flag is someone having the flare, and an ally having the Radar Jammer. That way enemies are completely unaware of your position.
 * If the player accidentally looks at an active flare, looking away will not completely get rid of the effects.
 * Using the Flare in campaign will sometimes make Grunts and Brutes dodge or panic, the Grunts fleeing and the Brutes rampaging.
 * The Flare, along with the Radar Jammer, is no longer available in matchmaking, due to a glitch with them that lets you jump higher to get to hidden spots but are still usable in Forge.
 * If the Flare is deployed to reach a large distance away from the user, and if the user can cope with a small lighting issue from the flare, the user can snipe opponents without them knowing where this is all happening, or knowing where the cover is. This can be especially good if the opponents have long range weapons to counter the Sniper Rifle or Beam Rifle.