Oh, that's nice... (Windows 10)

[#1]

Has anyone else come across a "surprise" feature, that wasn't made a big deal of in the media, but they find useful?
For me, it is that Windows finally has "scroll inactive windows when I hover over them" natively, like in OS X and most Linux distros. Once you get used to that way of working, it feels clunky to need to click in a window in order to scroll (particularly when you're working in multiple apps on multi-monitors).

[#2]

Copy and Paste shortcuts (CTRL+C/CTRL+V) now work in a command prompt.
By enabling the quick edit option, you can also highlight/copy text by mouse click/dragging as you would in any other application.

[#3]

Screen video recording. 
Designed for games, but works generally, including videos in the browser, iPlayer etc.  windows-g to get up the game menu, then press record button or use windows-alt-r
Works well for me: more reliable than Nvidia ShadowPlay or FRAPS (for me at least).