Impulse

A console command which can do lots of different stuff depending on its numeric parameter.

Here is a list. All those marked as a cheat will require sv_cheats to be enabled.

Gameplay impulses

These commands are used in-game by default.

impulse 50

Makes player command (call/send) a squad.
Default key: c

impulse 100

Toggles the flashlight on/off for the player.
Default key: f

Spawn Commands

impulse 82

Cheat. Spawns the buggy (and possibly something more, as the messages also talk about skulls and seagulls).

impulse 101

Commonly used cheat. Gives the player all weapons, extra ammo, extra health and extra energy.

impulse 102

Cheat. Spawns a human skull. (The models\Gibs\AGIBS.mdl gib.)

Other Commands

impulse 81

Cheat. Gives the player weapon_cubemap which is useful for checking cubemaps.

impulse 103

Cheat. Reports status (AI, health, etc.) of the NPC under the crosshairs.

impulse 106

Cheat. Displays the classname, targetname and modelname of the entity under the crosshairs.

impulse 107

Cheat. Prints what texture the crosshairs are pointing at.

impulse 108

Cheat. Debugs the NPC under the crosshairs.

impulse 200

Cheat. Toggles between lowering/raising the weapon, clearing it from the HUD, useful for taking screenshots.

impulse 203

Cheat. Remove the entity under the crosshairs.

Multiplayer games

impulse 201

Paints decal in multiplayer.
Default key: t

Half-Life: Source

impulse 71

Cheat. Spawns a npc_human_grunt

Nonfunctional

impulse 195

Cheat. Would show the shortest path in the level to the nearest node_viewer_fly node.

impulse 196

Cheat. Would show the shortest path in the level to the nearest node_viewer_large node.

impulse 197

Cheat. Would show the shortest path in the level to the nearest node_viewer_human node.

impulse 202

Would play 'player jingle'.

impulse 202

Cheat. Would splatter blood decal.