Castlevania: Circle of the Moon

1) Equip items with a combined strength penalty that is equal to or greater than your strength. While the game will indicate that you have 1 strength, actually having 1 strength is not enough to activate this glitch.
2) Activate the DSS card combo of your choice. Doesn't matter what it is - any DSS card combo will activate the glitch.

Once both conditions are met, attack power will instantly be raised to 99990 while both conditions hold true. While the game says that attack power is 9999, spinning the whip, which normally does 1/10th as much damage as striking with it, will also do 9999 damage when it hits, as if attack power was 99990 or higher. Unfortunately, actually using this glitch is basically impossible, due to the first requirement. The maximum attack power that you can have and still perform this trick is 210 (2 bear rings + dark armor), and, by the time you get these items, attack power will probably be far higher. Still, if you can pull it off, it's quite useful

You must have the Black Dog and Jupiter cards. When you are poisoned or cursed activate the Black Dog and Jupiter DSS combo. As soon as you activate it, deactivate it. You will now be poison or curse free.

When at the end of the Batlle Arena, where you get the Shinning Armor, Keep distance from the left wall and slide through the gap from a distance that you gon't fall out of it. You'll be at the entrance of the BA. Turn right and slide back in. The doors will be open. Keep killing until your health is low. You should gain a lot of exp. from the BA devil!