MAO produces the PAX-22 Tranquilizer Rifle, a single shot, break-action tranquilizer gun intended for use on animals, however they are sometimes used to incapacitate humans without killing them. MAO does not produce the darts, rather they are manufactured by Kaiga Incorporated.
The Widowmaker TX, a semi-automatic shotgun, is also produced by MAO. The TX is fed by a 6-round drum magazine, and can be modified in several ways, including a 2-round burst. This are a fairly popular shotgun, being used by several agencies such as the Detroit SWAT unit.
MAO is also known for producing Riot CS, or gas grenades. Riot CS knocks out organic enemies caught in the gas cloud after being thrown.
MAO also manufacture protection equipment, such as the hip pads used by some Belltower security guards, and the helmets worn by heavy troopers, all clearly marked with the company logo.
No such company exists in real world, but it may be an allusion to the real world company Česká Zbrojovka Uherský Brod (more commonly know simply as CZ or CZUB). This company is known for simple, but reliable and cheap small arms such as CZ 75 handgun (used by police forces around the world), Scorpion vz. 61 submachine gun, Sa vz. 58 assault rifle or more recently, CZ 805 Bren and CZ Scorpion Evo 3.