Hmm, I can think of a lot of boss fights that are on my least favorite list. Every one of them involves Seymour except one, the first Seymour fight at Macalania temple. This is where Yuna obtains my favorite aeon Shiva, and this fight is where she stands up for herself and finally listens to her heart. I like the fight probably because of where it ties in with the story. Yuna's guardians rush in to help her and once Yuna realizes that she isn't alone in dealing with Seymour, she takes a stand and the fight begins. This was probably a difficult decision that she thought about over and over again, until her guardians came and stood by her side. From that moment on, Yuna decides to listen to herself and continues to resist Seymour, even when he kidnaps her. It's a sign of self confidence that Yuna did not show before, and it was that moment that Tidus stepped in and decided to get involved.I guess this boss fight is memorable, because it represents a moment of strength for Yuna and an important decision for Tidus. At this point, they both decide to take charge of their lives and call the shots instead of do what everyone expects of them.