Final Fantasy

When you're on a boat, hold X and repeatedly tap Circle button (for the JP version, hold Circle and repeatedly tap X button). Then you should be able to play 15 Puzzle minigame.

This glitch will allow you to equip characters with normally-unusable weapons or armor and also generate and duplicate armor you already have (which can in turn be sold for endless amounts of Gil). To begin, enter the Configuration menu and change the cursor to Memory. From there, go to the Equip menu for a Warrior and select the slot you want to select equipment from. Next, place a unit next to the Warrior and select where the equipment will go to. Return to the Warrior's menu and the cursor should already be on the previously-selected slot. At this point, press L/R and X at the same time to switch to the recipient unit.

This can be done to give weapons to other characters that cannot wield these weapons, and the same for armor. More curiously, the glitch can be used to put weapons or armor in slots they are not meant to be in. This can either cause simple benefits (for example, equipping the Maximillian on the White Mage's head simply applies the boosts, though these boosts are much higher than normal for helms) or cause item transformations (such as making the Hammer turn into Knight's Armor).

Art Gallery allows you to view game art that you have unlocked.
Bestiary give you information on monsters that you have defeated.
Music Player allows you to play any BGM from the game.
Time Chamber allows you to revisit floors of Labyrinth of Time that you have already beaten.