Logitech MX Master (the original one). Which replaced a much loved, weighted, tweaked, repainted and endlessly used MS Intellimouse Explorer Wireless.
Love the Logitech - and the versatility of the extra buttons and Options. Obvious replacement would be either another one, or an MX Master 3 if and when the need comes, but as things stand, this one is still giving good battery life after four years of very heavy use, and hasn't suffered the problem with the wheel that was common enough to have YT videos showing how to fix.