Get a logitech MX518. It's silver and black, very comfortable and has an awesome sensor, and I think it'll match the iMac G5 just fine.
impierced said:I bought the, now shipping, Logitech® Cordless Desktop® S 530 Laser for Mac® and will admit I'm extremely happy with it.
Love the silver and white as it matches my Cinema display.
It's also the first Logitech product sold exclusive to the Mac market. Hell hath froze over.