Cheat mode:
     Successfully  complete  the  game  on  any  difficulty setting to
unlock  a  maze  mini-game  on  the  VMU.  Successfully  complete  the
maze-mini  game  to  unlock  a  cheat on the cheat menu. To access the
cheat  menu,  pause the game and choose the "Settings" selection, then
scroll  down  past  the  "Internet"  selection and choose the "Cheats"
selection. Depending on what difficulty the game was completed on will
depend  on  what  cheat  was  unlocked. Complete the game on different
difficulty settings to unlock different cheats.

Hidden Music:
     To play some hidden Quake 3 music turn on the Dreamcast without a
CD  in or with the lid open. At the Menu choose the music option, then
insert the Quake 3 disk (if you haven't already) and close teh lid. An
image  of  the  disk will appear and tracks four through nineteen will
play music from the game.