Open Steam, go to your "Play Games" menu,
and select Half-Life 2. Right click on it and select "Properties".
Click the Launch Options button then type -console. Click
"Ok", then close. Double click Half-Life 2 to start
the game. Once it is loaded and you are playing, press the ~
key to bring up the console. Then, enter sv_cheats 1 and
press [Enter]. You can now enter the following codes at
the console window.
Also, any code can be used as a command line parameter by prefixing
it with the "-" character.
Note: For games that were downloaded from Steam, to use cheats
in single player mode, start the game with the -applaunch -dev
-tconsole command line parameter.

Code
God mode (server only) god
Spawn indicated item give
Reduce your health buddha
Damage player hurtme
All weapons impulse 101
Skulls impulse 102
Spawn a jeep impulse 82
Spawn an air boat impulse 83
Spawn a scout car ch_createjeep
Spawn an airboat ch_createairboat
Ignored by NPCs notarget
Walk through objects (server only) noclip
List maps maps
Load indicated map map
Toggle developer mode; 2 is verbose developer
Enable mouse look +mlook
Show crosshairs hud_quickhelp/text? 1
Sets the size of carried weapon; 54 is default
viewmodel_fov
Execute script file exec
Toggle HUD display cl_drawhud
Toggle HUD display cl_enablehud
Toggle frame rate display cl_showfps
Creates an NPC; only where NPC are allowed
npc_create
Create an NPC aiming away from player npc_create_aimed
Toggle picker mode. picker
Set gravity value sv_gravity
Set minimum stopping speed when on ground
sv_stopspeed
Set world friction sv_friction
Set bounce multiplier for physically simulated objects collision
sv_bounce
Set maximum velocity of any moving object
sv_maxvelocity
Set vertical view fixup when eyes are near water plane
sv_waterdist
All chapters unlocked next time game is played
sv_unlocked chapters 15
Slow time; 1 is default cl_phys_timescale
Change air density air_density
Set length of explosion confusion dsp_explosion_effect_duration
See through walls mat_depthbias_normal 1
Disable dead bodies going through each other
cl_ragdoll_collide 1
Toggle bounding-boxes debug mode; red: ignore damage, white: respond to damage, green: health
prop_debug
Toggle reporting missing .WAV files sv_soundemitter_filecheck
Limits the number of texture units; 0 lets the game decide
mat_numtextureunits
Deleted targeted object or person impulse 203
Black and white screen mat_yuv 1
Color screen mat_yuv 0
Record demo record
Stop recording demo stop
Play recorded demo play