I will answer here and not the topic mentionned by Dori because the OP specifically said "that looks good with an iMac?".
I'm using the Pro|Click mouse from Razer. Bought it a couple years ago. I fits nicely with the aluminium keyboard and iMac.
The photo I linked above gives you a more realistic feel for its color, it's not as white as the photos on Razer's site.
After two years use I can say I'm very happy with it. The fabric on the body is great, it's a little shiny and perfectly smooth. The wheel and sides give off a nice bluey light. Coincidentally I'm using the Creative Gigaworks T20 external speakers, which also have a bright blue led on the front. So in the evening, they go rather nicely together ;)
My only complaint is the fabric of the buttons. There are yellowish patches where I place my fingers. EDIT: Which can not be easily cleaned, I precise ;) Unfortunately because the buttons are made of a different type of plastic, slightly rubberish. Personally I don't understand why they use rubbery buttons like that, but it's not a big deal.
The mouse is also very good for gaming, which is something to consider if you have gaming sessions with bootcamp.