Corsair M-65. I have large hands, so a bigger mouse helps. I like the little weights included- customisable so that gamers can find an ideal compromise between speed of reaction and lift. I just threw them all in! I like the 'sniper' button, the DPI adjustment on the fly and the extra side buttons. Mostly, I like the fact that it's still going strong after three years of hard use.
Previous failures included a Razer that wore out after about nineteen months- still the most expensive mouse I've ever owned- and a wireless RAT that was tiny and wouldn't stay linked to my PC, only a metre and a half away...
Honourable mention goes to my Maplins ergonomic mouse. It's a big, upright mouse, covered in soft rubber. My wrists were both broken a few years back. When it's damp and cold they get very sore, making it difficult to use a conventional mouse. The Maplins beastie is just the job. It's got some tidy features; it's wireless, has 3 DPI adjustments and two additional buttons. It's a good piece kit and very reasonably priced.
https://www.maplin.co.uk/p/maplin-pro-ergonomic-wireless-laser-mouse-n84dg