Go to the console by hitting tilde then type svcheats 1 to activate cheat mode.
Change maps by typing changelevel dust or any other map.
Now type any of the following codes at the console:
16,000 = impulse101
Arctic sniper rifle = givespaceweaponawp
Auto-aim with sniper = rifle svaim
Adjust gravity = svgravity [-999 - 999999]
See and fire through walls and objects = glzmax[0-9999]default value is 3600
Change lighting so you can see in dark =lambert -1.0001
View other players' frags = clhidefrags 0
Faster forward motion = clforwardspeed 999
Faster backwards motion = clbackspeed 999
Faster side motion = clsidespeed 999
Level select = changelevel [MAP NAME]
Weapon select = give weapon[WEAPON NAME]