Go to Options/Cheat Codes and enter one of the following codes :

 tumbler              :
 aquaspark            :
 starlite             : "hallucinating view"

 howhardcanitbe0      : Difficulty adjust (0 = easiest)
 howhardcanitbe1
 howhardcanitbe2
 howhardcanitbe3
 howhardcanitbe4
 howhardcanitbe5
 howhardcanitbe6
 howhardcanitbe7
 howhardcanitbe8
 howhardcanitbe9                           (9 = most difficult)

 starpower            : Gun (key F by default) and no damage
 happyhour            :
 leatherandlace       : Gun, rocket launcher (keys F and H) and no damage
 operationdoom        :
 upupdowndown         : Unlock all cities, vehicles and modes (arcade only)
 theparrot            : Unlock all modes
 griswold             : Unlock all cities
 quickFix             :
 octane               : Nitrous
 yerbamate            : Unlimited Nitrous
 rimbuk               : Unlock all cities, vehicles and modes (arcade only)

 howfastcanitbe0      : Speed adjust (0 = slowest)
 howfastcanitbe1
 howfastcanitbe2
 howfastcanitbe3
 howfastcanitbe4
 howfastcanitbe5
 howfastcanitbe6
 howfastcanitbe7
 howfastcanitbe8
 howfastcanitbe9                      (9 = fastest)

 Codes are case sensitive and be careful especially with AZERTY keyboard...