I liked Ghirahim on my first playthrough, I actually thought he was pretty tough. But once you get the hang of fighting him, he's a pushover. Just hold your sword to one side of him, then take it to the other side, and start swinging. *SPOILER* I enjoyed his character development, how he was Link's rival. And especially how he was the exact opposite of Fi, and how his sword form was an inverted version of the Master Sword. The final battle with him was pretty memorable, and one of my favorite bosses.