Secret of Mana
From SDA Knowledge Base
Few glitches to start off:
Glitches
Weapon Charge
Must have a level of 2 on a particular weapon (usually Sword or Spear). Set ACT on computer controlled character with weapon to charge to 1. After fully charged, set it in ACT to 2. As it starts charging, go to ACT again and change it back to 1. The weapon charge will glitch out. Chances are you can get a Level 8 charge attack, one-hit killing early bosses.
Infinite Money
Create a BLAT and sell 7 of those. I'm not entirely sure how this glitch works. Will fill out later.
Midge Mallet
Midge Mallet can be obtained any time after defeating Jabberwocky in the Water Palace. Useful for quick casting spells as well as nullifying damage/effects done by enemy spells.
Rope-pole Glitch
Something about hitting a rope pole as you call Flammie. Bypasses the Mana Fortress barrier, which in turn skips the entire Pure Lands.