Mortal Kombat

Hint: Defeating Goro and Shang Tsung:
Play as Scorpion and harpoon Goro (Away, Away, Low Punch) immediately following an uppercut (Away + Low Punch). Repeat this technique to defeat Goro and face Shang Tsung. Use the same technique to defeat him.
Information in this section was contributed by Seanofthedead12.

Hint: Fight against Reptile:
Look for shadows to appear across the moon in The Pit stage. If this happens, do the following steps. Do not press Block during the match. Have a Double Flawless victory against your opponent and finish him or her with a fatality. You can then fight Reptile at the bottom of the stage. Note: This cannot be done when playing as Sonya or Scorpion in v3.0 machines.

Glitch: Fight Goro without getting hurt:
On the stage before Goro pops out, back yourself into a corner. Allow your opponent to follow you there, then defeat them without using your fatality. Continue to hold Away and you should be walking backwards in place with your back in the corner. As Goro appears, continue holding Away. Immediately after Goro leans back to let out his scream, press Up + Away to backflip, then release the Joystick so that it goes back to its neutral position. Your character should backflip, then rise up and out of the screen leaving just your shadow on the playing field. You are now invincible when fighting Goro.
Information in this section was contributed by Brandon.