The G18 is the sidearm when using the Snowmobile in "Cliffhanger", or the Spec Ops missions, "Race" and "Time Trial". It can also be found in some of the levels such as "The Gulag" in the armory, "Takedown", "The Hornet's Nest," and "Loose Ends". It can also be found in akimbo variants in some levels. It is also found in a large number of Special Ops missions. The G18 is also the player's starting secondary weapon at the beginning of "The Hornets Nest".
The G18 is unlocked at Level 22 and has low damage, high recoil, a large 33 round magazine, and the highest rate of fire of all the guns in the game except the Vector which has a fire rate of 1,333 per minute with Rapid Fire. This high rate of fire makes Stopping Power of questionable use, because it only reduces the number of bullets needed to kill by 1.
The G18 is best used at close range because of its high recoil. A silencer makes the G18 an effective stealth sidearm and eliminates the large muzzle flash which can block the players view. It is widely regarded that Akimbo is the best attachment for the G18, as even without Steady Aim, the cross-hairs are one of the smallest of any Akimbo weapon, and the G18s high rate of fire makes this Akimbo pair devastating in close quarters, and even usable in medium ranges. However, using the G18 Akimbo is frowned upon by the majority of players because the relative ease of getting close to mid range kills. The G18 is an excellent compliment for riot shields, as the high fire rate and a relatively large magazine makes it deadly in close quarters, much like the default riot shield class which has the PP2000 Akimbo.
Due to the gun's nature, Marathon is a great perk to race to the enemy quickly. However, when using Akimbo G18s, Bling and Extended Magazines the player can quickly take out large amounts of players in close range veryquickly. Bling is also useful to pair Akimbo and the Silencer, removing muzzle flash and staying off of the minimap, while preserving the main advantage of Akimbo. Scavenger would be another good perk, as the G18's high rate of fire will burn through your ammo very quickly. Lightweight should be used with the G18, especially with Marathon, as Stopping Power is unnecessary due to the high rate of fire.