MP5K

The MP5K, also known as SMG1, is a weapon cut from Half-Life 2. It can be found in the playable Half-Life 2 Beta files.

The H&K MP5K is a compact version of German-designed SMG, the H&K MP5, with a shorter barrel making it even more maneuverable and more easily concealed.

The MP5K was apparently set to be HL2's primary SMG, and at some point during the development the MP5K and its replacement, the H&K MP7, existed side-by-side, but in the end it was cut in favour of the more modern MP7. Synergy and SMOD have a fully working version of the weapon.