Whoops, I thought I already posted (and that I saw it in the OP): I'm using a Logitech M570... wish they made these in Bluetooth, but the 'standard' RF is fine.
I can't imagine playing without it, although I guess it's whatever you develop muscle memory for. Cordless is nice for obvious reasons, and the trackball (really, any trackball) is nice because sometimes I like to kick back away from the desk, and I can put this on the arm rest of the chair and my (also wireless) keyboard on my lap. If I need the mouse to not move one bit, I just lift my thumb (no need to gingerly let go of the entire mouse). Also, I'm a lefty, but this is just what I've used ever since I started gaming. This particular model is an improvement over previous 'trackman marble' mice in terms of battery life (which went from like once every two months or so to I've only replaced it once since I got the mouse), and a couple of extra buttons. I was actually pretty concerned that Logitech was going to discontinue this line of mice entirely when they came out with this model.
Found this gem on eBay (UK) if anyone's interested - Logitech G5 (New) ~£25 They're pretty rare nowadays with being discontinued, so that price is a steal. Best mouse made, imo.