It's not on the list of headline features, but the latest version of Windows is hiding a very welcome and well-executed feature: a video-capture tool baked right into the operating system.
On previous versions of Windows, recording a video of your screen meant navigating the usual muddy creek of ad-infested freeware; the lack of integration also made setting up a keyboard command to start recording an exercise in frustration.
That's all changed with Windows 10, thanks to a video-record feature baked into the new Game DVR. Press Win+G, and a small bar pops up, with a video-capture button, and links to the Game DVR hub. (The first time you do this in a particular program, Windows will ask you to confirm that the program is a game, before starting Game DVR.)
Hit record (or Win+Alt+R), and it will automatically start capturing video from the program you've got open, rather than the entire screen. It's a feature aimed at gamers (duh) who want to share in-game clips, but it works equally well for sending your grandma a how-to video on using Google.
Even better for gamers: if you enable background recording, Game DVR will constantly record the last 30 seconds of activity in the background when you're playing a game. If something cool happens, hit Win+Alt+G, and it will save that 30-second snippet.
Also of mention is the new screen capture: Alt+Win+Print Screen now saves a screenshot of a window to the same folder. That might sound like a minor improvement, but it's a thousand times better than pasting Print-Screens into Paint like the XPers of yore, and even better than the Snipping Tool that ships on more recent versions of Windows.