Age: 16
Hometown: Wutai
Occupation: Materia Hunter
Weapon: Shuriken
Yuffie isn't going to start off with a good reputation. When you first meet her, she attacks you. If you you beat her AND you play your cards right, she'll join you. And even then, she's not entirely faithful. She's gonna do something that you'll want to kill her for, but after you chase her and find her, you'll find that it's all for the better. Yuffie is an interesting, but optional character. You're really better off with her. Besides, she'll get what's coming to her when you get the airship. She's not the strongest fighter, but she's not bad. She has pretty decent magic levels and her attacks aren't bad, either. She has some nifty early limit breaks (like one that heals everyone; she's the only character besides Aeris that has a healing limit break).
Where you meet her: In the first forest area you explore. See the FAQ for more details.
Level 4 Limit Break - All Creation
Yuffie shoots a large energy beam at all enemies, hitting them each for 9999 points of damage. You get All Creation if Yuffie can pass the five tests in the Wutai Pagoda after she rejoins your party.
Most Powerful Weapon - Conformer
You find this in the downed Shinra plane underwater. It's in the first room (go up from the save point). It's hard to find because it's hidden by an overhead beam. It's in the top left corber of the room. The Conformer gets an attack bonus based on the level of the enemy that it hits.