This is the Hammer FGD from 
Half-Life 2: Deathmatch.
- This is a FGD (Forge Game Data) file used to define all of the entities of a game for a map editor (such as Hammer).
To add a FGD file to the map editor, copy the following text into a text editor such as 
Notepad++, and save it with "save as type" being "all files" and .fgd appended to the file name. Then open your map editor and add the FGD to your game configuration.
Tip:Select the beginning of the line (usually the "//" comment) by clicking it, scroll down then hold ⇧ Shift, and click at the end of the line to select all.
FGD
This FGD file can be located here: 
.../common/Half-Life 2 Deathmatch/bin/hl2mp.fgd
//-------------------------------------------------------------------------
//
// Game data for Half-Life 2 Multiplayer.
//
//-------------------------------------------------------------------------
@include "halflife2.fgd"
@PointClass base(PlayerClass, Angles) studio("models/editor/playerstart.mdl") = info_player_deathmatch :
"This entity indicates the position and facing direction at which the player will spawn during a deathmatch map. Any number of "+
"info_player_deathmatch entities may be placed in a map."
[
]
@PointClass base(PlayerClass, Angles) studio("models/editor/playerstart.mdl") = info_player_combine :
"This entity indicates the position and facing direction at which the player will spawn during a deathmatch map. Any number of "+
"info_player_deathmatch entities may be placed in a map."
[
]
@PointClass base(PlayerClass, Angles) studio("models/editor/playerstart.mdl") = info_player_rebel :
"This entity indicates the position and facing direction at which the player will spawn during a deathmatch map. Any number of "+
"info_player_deathmatch entities may be placed in a map."
[
]
@FilterClass base(BaseFilter) size(-8 -8 -8, 8 8 8) = filter_activator_team :
"A filter that filters by the team of the activator."
[
filterteam(choices) : "Filter Team Number" : 2 :
"The team number to filter by. If the filter mode is Allow, only entities whose "+
"team number matches the given team will pass the filter. If the filter mode is Disallow, "+
"all entities EXCEPT those whose team number matches the given team will pass the filter." =
[
2 : "Combine"
3 : "Rebels"
]
]
@PointClass base(prop_physics) studioprop() sphere(fademindist) sphere(fademaxdist) = prop_physics_respawnable :
"This class is the same as prop_physics, except it respawns after it breaks"
[
RespawnTime(float) : "Respawn Time" : 60 : "Ammount in seconds this prop will respawn after it breaks."
]
@PointClass base(Weapon) studio("models/weapons/w_slam.mdl") = weapon_slam : "S.L.A.M. - Selectable Lightweight Attack Munition" []