M67 Grenade

The M67 fragmentation grenade is a small hand-held anti-personnel weapon in Call of Duty 4: Modern Warfare, Call of Duty 4: Modern Warfare (Nintendo DS), and Call of Duty: Modern Warfare 2 designed to be thrown, which then explodes after a short time.

Call of Duty: Modern Warfare
The frag can be used in several situations; learning how to effectively arc, bounce, and/or cook a grenade can make a player highly lethal (especially with the Frag x3 perk). In the game, the grenade functions like a concussion grenade (It emits no fragments, it only relies on explosive power) this has been done to balance the weapon. The frag grenade will usually kill the player if they see the frag indicator. If the player cooks the grenade long enough it will explode in the air when thrown; this can catch targets off-guard and gives them no time to react before the grenade detonates.

Experienced gamers know the "hotspots" (where players are most likely to frequent) of each map and will utilize this knowledge accordingly. If aimed properly, throwing the grenade up in the air will cause it to land on the path where enemies are still sprinting to gain a field advantage. This tactic could possibly end up in multiple kills, sometimes eviscerating two or even three opponents, giving the player's team an early UAV. It usually pays off not to be the person in front running for front lines. This tactic can be used in conjunction with the perks Frag x3 and Sonic Boom and is known as grenade mortaring. This tactic could also be used to lob frags toward a defended objective or a group of red dots, although experienced players will usually refrain from this tactic and use their frags more efficiently.

In the singleplayer campaign, the player spawns with four grenades and can find M67s in grenade bags dropped by some enemies.

Call of Duty: Modern Warfare (DS)
The DS variant is very similar to the console version. It can be cooked by holding the button down, but only for four seconds.

Call of Duty: Modern Warfare 2
Known in-game as the M2 Fragmentation grenade, the M67 grenade returns as the only fragmentation grenade, but this time it is in the Equipment category, which means the player can replace it with another weapon that is in the Equipment category. Players are now limited to a single frag grenade per life in multiplayer. However, if the player has equipped the Scavenger Perk, he can get multiple frag grenades. Infinity Ward has stated that new physics will be added to grenades to make them react to the environment more realistically (rolling them down a hill, for instance). A trail of smoke will also follow them when thrown. Frag grenades are useful for assaulting corridors and small, enclosed areas as players can bounce them into the desired location to kill enemy personnel or destroy equipment. Frag grenades are used uncommonly because Semtex is generally easier to use and more powerful.

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Trivia

 * The M67's texture sheet has the outline of a M26/M61 grenade, hinting that at one time, the player might've used a M61 grenade instead of a M67.
 * There is a mistake in Call of Duty: Modern Warfare 2; when the player runs out of grenades, a notification appears saying "No M2 Frag Grenade Ammo Available" when the grenades used are M67s. It is either a mistake or an easter egg, since all World War II games in the series use the Mk2 Grenade.
 * When throwing back a grenade, it shows the same animation as when a grenade is primed, which is impossible since the pin has already been pulled.
 * When using the Riot Shield, a well timed melee will bounce the grenade back towards enemies and kill them, counting as throwback kills.