From what I can remember, he's had about 4 changes to his black jacket. One, when he was twelve, had a zipper. Two, in the first episode, was actually more like a sleeveless shirt tucked into his belt. Three, the one with the clip we see most often. Four, the most recent one with the buckle-like things.
I've really started to fall in love with the fourth one. It makes him look more mature and stylish. The third one comes in a close second because it just screams "fantasy anime!" to me. ^^ And the zipper was very cute.
Btw, does anyone else notice the severe lack of red coat recently? I believe the only time we've seen it since episode 40 is in the Opening and Ending. ...I miss it. :(