Final Fantasy XII/DIY Sunstone

This sidequest is available after your party escapes from the Dreadnought Leviathan.

To start this sidequest, you have to go to the Nomad Village on the Giza Plains and speak to Masuya. She will ask if you want to make your own sunstone, and when you do you get given a Shadestone. The location of all active Dark Stones are marked on the map, so run to the one closest to it and hold up the Shadestone until it's a 100% Sunstone. Depending on how quick you were, you get different rewards as a result.

It isn't very difficult to make a high quality stone, so this is great if you're short a few gil for an aerodrome ride or want to gain a bit more LP.