During gameplay press Ctrl + Shift + '~' to bring up the cheat console and then type in the following lines without the quotes and press Ctrl + Shift + '~' again to enable the effect in the game (please note that on some keyboards the code may be ctrl + shift + @).
Toggle Fog of War (On/Off): Type the line 'FOW_Toggle'.
Enable Statgraph: Type the line 'statgraph()'.
Show FPS (Statgraph must be enabled): Type the line 'statgraph_channel('fps')'.
Set Game Speed (#=speed, 10=normal): Type the line 'setsimrate(#)'.
Show Taskbar: Type the line 'taskbar_show'.
Hide Taskbar: Type the line 'taskbar_hide'. Big Head Mode On: Type the line 'ee_bigheadmode(1)'.
Big Head Mode Off: Type the line 'ee_bigheadmode(0)'.
Remove Fog of War: Type the line 'FOW_RevealAll' (for this to be enabled the command-line parameter '-Dev' must be added to your game's shortcut).
Unlock ALL Missions: For this to be enabled you must add the command-line parameter '-unlock_all_missions' to your game's shortcut.