Cruis'n USA Cheats

Two player upgrade
Normally in two player mode, only one of the players can get an upgrade for their car. To upgrade both players, race to the Washington D.C., quit, and save the game. Reset the Nintendo 64, and have player one beat the Washington D.C. course. Reset the Nintendo 64 again, and have player two beat the same course. Both players will now have their cars upgraded.