The Mugen should definitely be in your list. I recently did an 8ight buggy for a friend of mine, and after having run it for about a month, he's selling it. He just can't get the hang of the way it handles. After my having gotten the Muggy converted, he's decided to go with the MBX5 Truggy. It handles well and does it easily.

Personally, if I were to do another buggy, it would have to be the X-Ray. Those things make even me look good.