Have Vincent join your party

Use a summon Materia in battle

Get Don Corneo to choose Cloud over the two females

Use a Limit Break

Finish the game

Beat the Omega Weapon

Complete the Obel Lake side quest

Upgrade your weapon

Reach maximum HP

Unlock Guardian Force Bahamut

Reach SeeD rank A

Collect all Timber Maniacs magazines

Unlock Guardian Force Cerberus