Pause the game and enter a cheat. All codes work on the latest patch (so get one).
Bouncy suspensions/boundaries ... bouncy
Abnormally good traction ... sticky
Abnormally bad traction ... slippery
Double game speed ... turbo
Infinite bottle rockets ... war
Disable collisions ... ghost
CPU drivers get road rage ... hitme
Track hazards missing ... bugoff
Low gravity ... moon
High gravity ... heavy
NDS ROMS 
GBA ROMS
NES ROMS
SNES ROMS
N64 ROMS
NEOGEO ROMS
SATURN ROMS 
DREAMCAST ROMS
CPS1 ROMS
CPS2 ROMS
MAME ROMS