Tokyo Xtreme Racer 2 is the sequel to Tokyo Xtreme Racer which is also on the Sega Dreamcast. Tokyo Xtreme Racer 2 has been enhanced with better sound quality and graphics over its predecessor. This game managed to produce two more sequels. This is the last game in the series that was produced for Sega.
Using the Gameshark code which enables all cars to be available for purchase from the start of the game causes extra cars to become available that so far have not been found through any other method and there appears to be virtually no information online about these hidden cars. The majority of them look like Mitsubishi GTOs (American made Mitsubishi GTOs are called 3000GTs) that appear to float above the ground for no given reason although the description for each car suggests that many are not at all Mitsubishi GTOs and in some cases not even any kind of Mitsubishi car. There is one more hidden car that is shown as it is supposed to look, the 100MV. The extra cars are obviously not a glitch as they have their own unique descriptions and attributes but there seems to be no knowledge of how to acquire or even encounter any of these cars without the Gameshark code.
Source: Wikipedia, "Tokyo Xtreme Racer 2", available under the CC-BY-SA License.