In the registered version, type "xacman" at the menu screen to play a subgame
similar to Pac-Man.

Also in the registered version, you can fight the secret boss Blarney by
typing "blarney" at any menu screen.

Other tricks can be done with the XPR.INI file:  change BloodVolume to 499998
to get more blood than even the BLOOD cheat code.  Change "Type" in both the
FPPlayer1 and FPPlayer2 sections to "2" (the joystick) to get your opponent to
mirror your punches and kicks (but not movement).