Question mark menu:
Hold Up + Block + Run at the options screen until it shakes.

Classic characters:
Highlight Jax, Kano, Kung Lao or Raiden, then press 7 or X.

Stage select:
Highlight Sonya Blade at the character selection screen. Hold [Up] + [Enter] or [Up] + Z. The screen will shake to confirm correct code entry.

Fight as Chameleon:
Choose any male ninja (Reptile, Classic Sub-Zero, Rain, Human Smoke, Ermac, Noob Saibot, or Scorpion) and hold (Back) + (LP) + (HP) until the fight starts. Chameleon is a semi-clear ninja that morphs into all the other ninjas in the game. When the fight begins, your ninja will explode and change into Chameleon.

Debug coordinates:
Press N during game play.

One button endings:
Start the game with the mkrtilw -f_1butt command line. Then, press one of the following keys at the "Finish Him" screen:

High Punch: Brutality
Low Punch: Babality
High Kick: Fatality 1
Low Kick: Fatality 2
Block: Friendship
Run: Animality

Instant kill (Windows version):
Start the game with the mktrilw -instykill command line. Press [F1] to kill player one or [F2] to kill player two.

View all command line cheats (Windows version):
Start the game with the mktrilw -povhelp command line.

Enable treasure chest (DOS version):
Start the game with the mktril.exe /treasure command line.  

Kombat Kodes:
Enter one of the following Kombat Kodes to activate the corresponding effect.

Result: Kombat Kode:

Throwing encouraged: 010-010
No throws; 100-100
No blocking: 020-020
Silent Kombat: 300-300
Quick uppercut recovery: 788-322
50% energy for player 1: 033-000
50% energy for player 2: 000-033
25% energy for player 1: 707-000
25% energy for player 2: 000-707
Sans power: 044-440
Dark fighting: 688-422
Unlimited run: 466-466