On the high score table type any of the following for your initials:
"HSC"____________________FOR INFINITE LIVES.
"KDJ"_____________________FOR INVINCIBILITY.
"RHL"__________________________FOR ACID MEN.
"JGL"____________________FOR FULL FIREPOWER.
"RAB"______________________________NOT SURE.
Note that you enter the first two letters as normal, then press and
hold '5' on the numerical keypad, then enter the third letter to
register the cheat.