Regen bug

The Regen bug is an exploitable glitch in FFVII. First, you cast regen on any or all of your party members. Then you open your disc tray so the game does not process any more battle actions. The game does not run until the disc tray is closed, but your characters will continue to regain their health through the regen effect. Effectively, you can cast regen, take an attack, then open the disc tray to regain all your health.