cmack,
I would go with a branching type hammer. The regular hammers are much harder to keep. I have had both, and the branching hammer is still with me. I was told by the LFS I got it from that if anythign happens to one head, just snap it off, and the others will be fine. It has never come to that, but I have seen the regular hammers just have problems and receed into oblivion.
Hammers like lots of water movement, lots of light, calcium and feeding. Get a good looking green one. I have cream one, which is pretty, but the green ones, as you can see from the pictures, are really beautiful.