Winning the Turtle Paradise contest gets you a Power Source, Guard Source, Magic Source, Mind Source, Speed Source, Luck Source, and Megalixer if you get all the flyers and talk to the owner of Turtle's Paradise in Wutai Village.

Flyer Locations:
1) Sector 5 Slum, in a house to the east, in a boy's room
2) In the Shinra Headquarters at the back of the lobby
3) Ghost Hotel at the Gold Saucer, near the item shop
4) Tiger Lily Arms Shop in Cosmo Canyon near the owner
5) Cosmo Canyon Inn
6) Near Turtle's Paradise in Yuffie's basement near the trap room