PPS:
Hotkey Alt+F1 forces Invincible mode for Niko do not lose it after cutscenes. maybe it can eat CPU so use it on your own decision instead of normal Invincible option.
Hotkey TAB allows you to save anywhere if Niko is on foot.
Hotkey CTRL+SPACE toogles/untoogles special Bullet mode.
Hotkey F1 toogles Ingame menu.
Hotkey F2 toogles additional info.
Hotkey F3 toogles speedometer.
Hotkey Num0 instantly boosts your car up to value InstantSpeedupVal from snt.ini section Misc.