Carmaggedon

In the menu with Map Select, Vehicle Select, Start Race, and so on, type ENABLE (quickly) to be given access to all tracks and vehicles. This will enable cheating. When the race starts use F4 to cycle through the modes until CHEAT MODE appears. Then all the following cheats will become available:

F5	total repair for free
F6	toggle Invulnerability on/off
F7	adds 30 seconds to the timer
F8	freeze/unfreeze timer
F10	increment lap counter
F11	earn 5,000 credits instantly
F12	switch between each opponent's camera and your own
Shift-F6	shows all opponents on the map
Shift-F7	adds 300 seconds to timer
Shift-F8	toggles shadowing between none/your car only/all cars
Shift-F10	increment checkpoint counter
Shift-F11	lose 5,000 credits instantly
Ctrl-F8	toggles shadow between solid (faster performance) and translucent
Ctrl-Keypad 1	toggles Fly mode

PowerUps (the code comes before the details)

0 bonus 1 megabonus 2 pedestrians glued to ground 3 giant pedestrians 4 explosive pedestrians 5 hot rod 6 turbo pedestrians 7 Invulnerability 8 free repairs 9 instant repairs Shift-0 timer frozen Shift-1 underwater ability Shift-2 time bonus Shift-3 body work trashed Shift-4 blow yourself up Shift-5 frozen opponents Shift-6 frozen cops Shift-7 turbo opponents Shift-8 turbo cops Shift-9 gravity goes strange Alt-0 pinball mode Alt-1 wall climbing Alt-2 bouncy-bouncy Alt-3 jelly suspension Alt-4 pedestrians show up on map Alt-5 pedestrian Extro-Bastard ray Alt-6 greasy tires Alt-7 damage magnifier Shift-Alt-2 instant handbrake Shift-Alt-4 turbo! Shift-Alt-5 megaturbo!! Shift-Alt-6 blind pedestrians (honk your horn at them!) Shift-Alt-7 pedestrians respawn Shift-Alt-8-5 free recovery vouchers Shift-Alt-9 solid granite car! Ctrl-0 rock springs! Ctrl-1 drugs! Ctrl-2 grip-o-matic tires Ctrl-3 pedestrian harvest