MP5-K is a beta weapon in GTA San Andreas.
The MP5-K appears in the game's files using the same camouflaged texture present on the M16A1 during the mission Stowaway, during which, a box labeled "MP5-Ks" can be found. The models themselves are ripped directly from GTA Vice City. Also, these boxes also appear in the previous mission, Catalyst. The model still exists in gta_int.img called "cj_mp5k.dff."