For Classic (that is, OS 9 and below) Macs, the best mice i've ever used are the ADB Mouse II, or the Pro Mouse.

For PS/2 and USB computers, either of my MS wireless mice, a Microsoft Wireless Wheel Mouse (PS/2, but can be connected to USB via a USB -> PS/2 adaptor, or a Microsoft Mobile Memory Mouse 8000 (which works on either USB or bluetooth)