打出の小槌 / うちでのこづち [uchide no kozuchi] in Japanese. The Japanese name of the item refers to the 'miracle mallet' in the legend of Once-Inch Boy. In the legend, an oni (a demon of sorts) that the one-inch boy defeats drops the mallet, and the princess he saved uses the hammer to make the boy normal-sized.
Final Fantasy II
Buy: 60 gil (sell: 30 gil)
Other: Cures Amnesia
Final Fantasy III

Buy: 100 gil (sell: ? gil)
Shop: Village of the Ancients, Dwarven Hollows, Amur, Duster, Saronia NW, Doga's Manor, Ancient Ruins
Drop/Steal: Blood Bat, Pugman
Treasure: Canaan
Type: Consumable
Effect: Removes or applies Mini
Final Fantasy IV
Final Fantasy V
Buy: 50 gil (Sell: 25 gil)
Obtain: some chests
Other: cures Mini
Final Fantasy VII

Buy: 150 gil (sell: ? gil)
Shop: Cosmo Canyon, Gongaga, Gold Saucer, North Corel
Effect: cures Mini
Other: as 'Cornucopia'
Final Fantasy XII
Buy: - (sell: 2,498 gil)
Use: Masamune
Drop: Purobolos
Steal: Bombshell
Poach: Purobolos
Obtain: defeat the King Bomb and talk to Montblanc
Description: This handy tool, called a gavel by some aritificers, is said to have once been used to restore order in courtrooms in ancient times.
Final Fantasy XIII-2
Buy: ? gil (sell: ? gil)
Obtain: various spheres
Description: Removes Fog from one ally
Category: Item