Not just the notification bar. I get spammed every time I start a game with little popups telling me various keys I can push to access Windows features while I'm in the game. (_Every_ time. The same notifications). I get spammed _during_ gaming with popups telling me to install Skype or some other Microsoft product. Plus all the spam on the lock screen about using a Windows phone (I haven't even _seen_ anyone with a Windows phone in five years).

Of all the obnoxious things with Windows 10 there was nothing that made my blood boil more than being in the middle of a competitive Overwatch match and have Windows pop up over my screen telling me to install Skype.

(The second place award goes to when I was using one of those early developer builds of Windows 10 and the license expired. Next time I booted the machine it booted into a blue screen telling me that, because it had expired, they went ahead and deleted a system file that made the OS impossible to boot. The exact details are fuzzy now, but that's the gist of it. I'm seriously not making that up. Important system file deleted; OS dead)