When in the game, press ~ to display the console window and then enter one of the following codes:
Level select: unlock all
Invincibility for player: god
Invincibility for team: godteam
Invincibility for terrorists: godterro
Invincibility for hostages: godhostage 1
Invincibility for hostages disabled: godhostage 2
Activates all the god modes: godall
Full ammunition: fullammo
Toggle third person view: behindview [0 or 1]
Flight mode: ghost
Disable flight mode: walk
Record demo of current game demo: rec [filename]
Stops demo recording: stopdemo
Play indicated demo: demoplay [filename]