Go to the console by hitting tilde (~) then type sv_cheats 1 to activate cheat mode. Change maps by typing changelevel dust (or any other map).

Cheat codes:

$16,000 = impulse101

Arctic sniper rifle = givespaceweapon_awp

Auto-aim with sniper = rifle sv_aim

Adjust gravity = sv_gravity [-999 - 999999]

See and fire through walls and objects = gl_zmax[0-9999](default value is 3600)

Change lighting so you can see in dark =lambert -1.0001

View other players' frags = cl_hidefrags 0

Faster forward motion = cl_forwardspeed 999

Faster backwards motion = cl_backspeed 999

Faster side motion = cl_sidespeed 999

Level select = changelevel [MAP NAME]

Weapon select = give weapon_[WEAPON NAME]