M9 fragmentation grenade

The UNSC-issued M9 High-Explosive Dual-Purpose Grenade (abbreviated M9 HE-DP Grenade), the Fragmentation Grenade, also known as the Frag Grenade to most players, functions in a manner very similar to contemporary hand grenades. When thrown, a blast bursts the grenade's shell open and sends small metal fragments flying at high speed, causing damage to everything in a nine meter (30ft) radius. In Halo: Combat Evolved and Halo 2, Four of these grenades could be carried at a time. This was reduced in Halo 3 to only two due to the presence of 4 grenade types and balance issues.

Description
HE-DP stands for High-Explosive Dual-Purpose. The first phrase indicates the grenade uses a high-explosive substance to launch its shrapnel when the grenade explodes, while the second means it can be used against both infantry and vehicles (hence "dual-purpose").

The grenade has a hard metal casing that is smooth in Halo: Combat Evolved, but has a grided surface in Halo 2 and Halo 3. This griding is most likely used to provide a better grip for the thrower, and would not influence the fragmentation pattern of its shrapnel. Instead, the grenade's outer metal casing, presumably made of steel or another hard metal (such as tungsten) or an alloy, would be blown to pieces when the HE core inside detonates.

AP FRAG can be viewed on the Halo: Combat Evolved M9's olive casing. AP most likely stands for "anti-personnel", indicating the shrapnel of the grenade can penetrate lightly armoured infantry.

In all Halo games, the grenade must first hit the ground before exploding. In Halo 1, the grenade would not detonate mid-air. In Halo 2 and Halo 3, it would bounce and explode mid-air a moment after bouncing. But in Halo 3, if the grenade was thrown up, and hit a surface going up, it wouldn't explode until it hit the ground. This presumed to be a safety feature, ensuring the grenade would only explode after striking a surface after being thrown, and not in the user's hand.

This may explain the lack of a "spoon", or handle, on the Halo 2 and 3 M9 HE-DP grenades. The spoon is a device that is gripped while the grenade is being primed, and ensures it will not explode until after the spoon is released, as it starts the fuse of a grenade as it flies through the air after it is thrown. In Halo 1, the spoon would have negated the need for this Halo 2 safety feature.

It is unknown how the M9 is first primed, but references to pulling a pin on the grenade is mentioned in the Halo novels several times, even though no pin is visible in game play. However, pulling a pin would require two hands, but each version of the grenade has a button on its body. This would most likely be pushed to prime the M9 before tossing it. The pin reference is most likely an inaccuracy on the author's part in the novels, or perhaps just a turn of phrase that has lingered from more primitive grenade types.

In Halo: Combat Evolved the fragmentation grenade left a white smoke trail behind it when thrown and would create sparks when it landed after being hurled.

Advantages
This grenade, can be effectively hurled and bounced around corners and travels farther than the Plasma Grenade, this can be used to quickly and aptly damage an attacker before he can move away from it, giving you an instant advantage in the combat situation. It is also harder to see and has a shorter fuse, therefore making it harder to avoid and more useful for killing enemies on foot. In Halo: Combat Evolved, it also seems to have a larger blast radius, than a plasma grenade. It has a further casualty range than the other grenade types in Halo 3. Also, since it is harder to see, having an enemy run over one by accident can happen more easily than with a bright blue plasma grenade. Also, they are extremely common, as all health packs in Halo: CE have fragmentation grenades beside them and all Marines carry them.

One of the best tactics to use, is to first throw a Frag, and then simply cut the shieldless opponent down with a weapon of your choice, preferably human due to its effectiveness in taking out flesh (rather than shields).

Disadvantages
Unlike the Plasma grenade, this grenade doesn't stick to objects, making it harder to hit vehicles. In Halo 3, it deals slightly less damage than the Covenant Plasma Grenade and Spike Grenade. In addition, if too close, you will be hurt just as much as the opponent. Last but definitely not least; it cannot kill a shielded Elite, Spartan, or Brute, no matter the range. In stark contrast, the Plasma Grenade is a one-hit kill if stuck or lands nearby so you have to be careful when throwing. Also when you throw the grenade the enemy might run to you making the frag grenade throw a useless move.

Campaign
The M9 HE-DP Grenade is best used when enemies gather together in tight groups. A well thrown grenade placed in the middle of a squad of Elites and Grunts will kill most of the Grunts and damage the Elite's Shields; however, a single grenade cannot kill even a Minor Elite, but just damage its shields The only Elites that can be killed with one is a Stealth Elite. Grunts may also panic and flee making them easy targets for follow up attacks. Frag grenades may be used against Jackals, as their Shields will not protect them from the blast. The M9 HE-DP Grenade is also commonly used to disable most land vehicles with the exception of tanks.

There is a useful tactic that can be used to take down a group of Grunts and Elites. It requires a frag grenade and a plasma pistol. Throw the frag grenade into a middle of the clump, and then build up an overcharged blast with your plasma pistol. Hit the lead Elite with the overcharged blast. The overcharge will knock out the Elite's shield just before the grenade detonates, which should kill the Elite as well as at least most of the Grunts. Any grenade can work for this tactic, but a frag is optimal.

Multiplayer
A multipurpose weapon, the fragmentation grenade can be used in corridors, to flush out occupants. The blast will severely damage player's Energy Shields allowing for easy follow up attacks. If lobbed under a vehicle, the explosion will either kill or severely injure the occupants. If timed correctly, grenades can be planted in the path of an oncoming vehicle. Most drivers will not be able to react quickly enough, and will most likely be caught in the blast. If you place the grenade under an enemy it will kill them. Note: This is very hard to do and it only works in Halo 2. Another good multiplayer tactic is to throw one at your feet while back-pedalling when an enemy is charging at you. When the grenade detonates, the other person should be in the blast radius of the grenade and be killed; if not, use a headshot on them, as their shields should be down. It can be done with other grenades, but as the frag grenade is the hardest to see, it is unlikely that the other person will dodge it. It also has a bigger blast radius. This is easiest done in Halo: Combat Evolved. In some maps like Snowbound and Sandtrap, if a frag is thrown it will stay where it lands given the soft nature of the ground on both maps. This is useful to fight oncoming vehicles, preferably lighter vehicles like Ghosts and Mongooses or even heavier vehicles like Warthogs. One frag grenade is considered as either aid in combat for quick damage before the fight starts, or as a tool to finish off an unshielded opponent. A grenade can be bounced off of a wall to ambush an enemy or ambush your ambushers. Two frags is where this grenade becomes a killer all on its own. Frags are also very handy to kill opponents when used in conjunction with explosive objects, waiting to destroy fusion coils with a grenade means the frags damage plus the coils damage would make a very dangerous environment for the target. On Narrows, one useful tactic is at the beginning of the battle, go off the man cannon and throw a grenade onto the middle of the bridge. Usually, people have already advanced on the bridge and have their shields severely disabled or taken out completely. The grenade will then kill them. This is great for getting an easy kill at the beginning of a match. When outside on Snowbound, the grenades don't bounce in the snow; they embed into it. This is semi-useless, but it's something that most people wouldn't know. A tactic done by most players is to clear areas by throwing frags and bouncing them off walls. This is effective in games like King of the Hill where you can throw grenades into the hill, to force the enemy out or to weaken them for a quick kill. It's best to know the map for bouncing the grenade off walls and objects. Also look for spots above or below your target, to be a little sneaky.

Trivia

 * The cost of a Spartan Laser is that of 7,895 Frag grenades.
 * The grenade can be used for a Warthog Jump.
 * These are commonly used for grenade jumps.
 * It is possible to wedge or throw a frag grenade in a vehicle or a Sentinel, though this rarely occurs. If you are attempting this stunt, try the Warthog. For other vehicles, such as the Ghost, the grenade will generally (no glitches) slip out.
 * The Frag Grenade is useful for clearing out corners without going into the crossfire.
 * By crouching and looking down if a frag grenade is thrown it will go under the players foot, a good strategy for grenade jumping.
 * In Halo 2, if you throw a grenade (when you don't have any) while looking down your torso appears to rise from your hips.
 * In Halo 2 and 3 you can shoot frags out of the air. The best weapon to do this is the Battle Rifle. In Halo 2, after it blows up you can see the grenade fly off still in one piece.
 * With full shields it is impossible to die from a frag detonation, in Halo 2 and Halo 3 the detonation would knock out shields and armour and sometimes cause blood loss, in Halo: Combat Evolved a fragmentation grenade would knock out the shields and leave only three health bars.
 * Shooting the grenade as it is thrown with a Battle Rifle could result in an easy two shot kill (hitting the grenade then finishing with a head shot).
 * The Frag Grenade can be used to nab an easy Double Kill, especially in a swords match where two player's shields may be down.
 * Using the Frag grenade, one could throw it up a grav lift to prevent "lift campers."
 * It is rather difficult, but you can get a frag stuck in a grav lifts gravity stream.
 * In Halo 3, if the frag is thrown up and hits a surface, it won’t explode until it lands. This is unusual because once it hits a surface, its supposed to explode a few seconds later.
 * It is possible to stick a frag grenade with a plasma grenade if the Plasma Grenade is stuck on the players left hand before throwing a frag, eventually throwing the frag with the plasma grenade stuck to it, or if they both simply collide in the air and blow up between the two players (which is very, very unlikely).This can also be done with a spike grenade.
 * It is possible to "stick" a person with a frag grenade, but it is really difficult. It has to land between their arms so they "cradle" it.
 * In Halo 3, according to the game manual, the frag grenade has the highest kill radius (5m), and the highest casualty radius (15m) of all the grenades in the game.