Double-clicking and dragging selects text word-by-word.
Triple-clicking selects the whole paragraph.
Middle-clicking a link opens it in a new tab.
Middle-clicking a tab closes it.
Middle-clicking in general often has useful functionality!
Ctrl+Arrow keys navigates through whole words at a time
Ctrl+Shift+Arrow keys can be combined to select whole words
Ctrl+Backspace can be used to delete whole words
I may or may not use this with my laptop dozens of times a day (it's how I copy/paste out of xterm).
(Fun bit of trivia, my old EliteBook 8470p has a trackpad+trackpoint setup with two independent sets of buttons, and while I don't seem to be able to middle-click with the trackpoint buttons, I can send a middle-click by pressing both trackpad buttons, keep them held down, and then independently send left and right clicks (press-release) using the trackpoint buttons as much as I want. I somehow doubt that was an accident. Engineering archaeology is fun :D)
In code-editors tripple selects a line (hold to select multiple). When moving/deleting lines this is much more semantically clean (and faster) than manually dragging from the previous line's line end to the next lines last character before the line end.
When I wrote about the double-click-drag thing, I thought triple-click-drag might logically also be a thing, but it doesn't work for me. (Firefox, KDE, Linux)
Ahh I used a Magic Mouse and trackpad for so long I forgot about this. It makes me a little sad. On the other hand panning and gestures are worth the loss.