'''David M. Mertz''' was writer and game developer for Gearbox Software. With Rob Heironimus and Randy Pitchford, he co-wrote the story for ''Half-Life Blue Shift''. He also designed the Santego Military Base for ''Half-Life Opposing Force'' and several ''Blue Shift'' levels.http//www.mobygames.com/developer/sheet/view/developerId,22311/ MobyGames profile
*In the room right below Shephard's dormitory (only accessed by noclipping) can be found an Easter egg, consisting in initials and a date ("DMM 1999"). "DMM" is the signature of David M. Mertz; "1999" is the release date for ''Opposing Force''. Mertz wchaloDMM 2003|did it again for ''wchaloHalo PC|Halo PC'' in 2003 (''Halo'' ported for the PC by Gearbox), in the multiplayer map ''wchaloTimberland (Level)|Timberland'', where he signed "DMM 2003" behind a group of trees.
*With other Gearbox employees, he gave his name to an D. Mertz|HECU recruit seen in Santego Military Base in ''Half-Life Opposing Force'' and a Mertz (scientist)|Black Mesa scientist accommodated in the Level 3 Dormitories in the Black Mesa Research Facility|Black Mesa South Wing featured in ''Half-Life Decay''.
FileDmm bootcamp 1.jpg|Mertz's signature in Santego's hidden room.
FileDmm bootcamp 2.jpg|Ditto.