For the classic Mac OS, either the ADB Mouse II or the Pro Mouse (black). For other systems...i personally really quite like my Microsoft Mobile Memory Mouse 8000, its a little wireless notebook mouse that can switch between either RF and bluetooth. I personally can't stand most "mini-mice", but this one is actually really quite comfortable, fits into your hand really well, and since it supports RF (and therefore has a dongle) runs on any computer that supports a USB HID device. Really, pretty much anything Microsoft is good, even their old ball mice are damn good, if you ask me.