Virtua Cop 

In the middle of the game, 
press pause and type "BANG". 

play as gold dural
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In the character selection menu, press 
DOWN, UP, RIGHT, then DEL+LEFT. 
You should here a confirming sound 

play as silver dural
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In the character select menu, press 
DOWN, UP, RIGHT, then DEL+LEFT 

add dural to the records screen
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At the start screen, press UP 17 times, 
then press ENTER. Go to the options screen, 
and you should hear "RING OUT!". 

slow motion replaying
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At the end of the round, hold 
DEL+END+PGDN before the character does 
their victory stand 

choose victory phrase
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Hold either DEL, END or PGDN, 
and you can choose 

stage select and ring size
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At the start screen, press UP 12 times, and 
press ENTER. Go to the options menu, and you 
should here "K.O.!". Move the cursor to the 
exit, and press down once more to make the 
cursor disappear. 
Press DEL and a second options menu will appear.