One of my favorite machines for classic Mac gaming is the first iteration of the iMac G4 (700/800mhz) , which allows booting into OS 9. Not only is it an amazing form factor, it's got a great screen and the official speakers are really nice. It's the complete package for a great gaming experience. The machine is powerful enough to run any game prior to its release (and so many after, of course). It's also a great conversation piece when it's not actively in use! :)