It's not that well known, but the Limit Breaks from Final Fantasy VII were based on a hidden mechanic from the previous game. When a character's health was less than 1/8 maximum, there was a 1 in 16 chance that choosing to attack as normal would instead unleash a hidden ability unique to each.

See, for example, Cyan's Tsubame Gaeshi. The veteran samurai draws upon his most intensive training to perform the Turning Swallow Cut: a swift downward slash, followed by a lethal upstroke. His blade moves so swiftly that it transcends the physical and deals magic damage instead.

Credit where credit is due: the background is from the game itself (Doma Castle, where Cyan makes one last hopeless stand in defending his liege against the Gestahlian Empire); character and game are (c) Squaresoft/Square-Enix.

This was the one where I discovered that Yoshitaka Amano isn't all that concerned with consistency between character sketches, so I kinda had to make a composite of all the different ways Cyan's armor was depicted from different angles and (as is my tradition) still managed to get parts of it wrong. Maybe I should just claim it's an homage to Amano's own variable ways.