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Do that many people really just read the subject without actually reading what original posters post? It's a 10 year old kid playing mine craft.... and the OP doesn't want a dongle.

I'd just get any cheap bluetooth mouse. Even the cheapest mouse will be better for gaming than any Apple mouse.

^This.

I had a spare Microsoft bluetooth "laptop" mouse - one of those that's smaller than a normal mouse - laying around and gave it to my daughter to use when I upgraded my iMac and gave her my old one. It works great. Any bluetooth mouse should work without the need to add a dongle. Wireless input devices (non-BT) need dongles, and computers w/o built-in BT need dongles for BT devices, but you should be fine with any inexpensive BT mouse. Microsoft and Logitech for sure make those small BT mice that are meant for travel purposes that would likely fit your son's hand really well. Plus they have on/off switches so when he isn't using it you can switch it off and save battery life. Both should be able to coexist happily; I use a Razer mouse for gaming (corded) and a magic mouse for casual use. I can go back and forth seamlessly without having to do anything special. No reason 2 BT mice couldn't do the same.
 
Some options in here as I initially stated a gaming mouse are way way to expensive, eg the mx518 is £130 here in UK!!! I should have worded it better maybe

I'm after a mouse that will work wirelessly via Bluetooth with no dongles on my iMac. Has any of the above been used on iMacs and work fine?

Thanks

Razor Orochi, plus when you're gaming you can use a removable (included) USB cable as to overcome Bluetooth lag.
 
I'm using a Razer Naga Molten. Cat fur can mess up the tracking, but aside from that I've been happy with it.
 
any wired USB mouse will do :)

wireless will have slight lag, no matter what even if on desktop seems fine.
 
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