MP

MP can refer to Multiplayer or Machine Pistol. It is also part of the name of several weapons:
*MP5 - A submachine gun that appears in several games.
*MP5K - The compact variant in Call of Duty: Modern Warfare 2, Call of Duty: Black Ops, Call of Duty: Black Ops: Declassified and Call of Duty Online.
*MP7 - A submachine gun appearing in some games of the Modern Warfare series, as well as in Call of Duty: Black Ops II, Call of Duty Online and Call of Duty: Mobile.
*MP9 - A machine pistol/submachine gun in Call of Duty: Modern Warfare 3 and Call of Duty: Modern Warfare III.
*MP11 - A submachine gun Call of Duty: Advanced Warfare.
*MP40 - A submachine gun that appears in all World War II installments of the series, as well as in most of the Black Ops series and in Advanced Warfare.
*MP44/StG-44 - An assault rifle that appears in all World War II installments of the series except Call of Duty: Finest Hour, and also appearing in Call of Duty 4: Modern Warfare, Black Ops, Black Ops II, Advanced Warfare and Call of Duty: Black Ops III.
*MP412 - A revolver in Modern Warfare 3.
*MP-443 Grach - A pistol in Call of Duty: Ghosts and Advanced Warfare.
*MPL - A submachine gun in Black Ops.
*TMP - A machine pistol in Modern Warfare 2 and Online.
*UMP45 - A submachine gun in Modern Warfare 2, Modern Warfare 3, Online, Call of Duty: Infinite Warfare and Modern Warfare III.
*VMP - A submachine gun in Black Ops III and Call of Duty: Black Ops 4.
*EMP44 - A submachine gun in Call of Duty: WWII.
*Erma EMP - A submachine gun in Call of Duty: WWII.
*AMP63 - The PM63 as it is called in Call of Duty: Black Ops Cold War.