I was messing around today and accidentally discovered that pressing the Windows key and a number will switch to the item in the corresponding position on the taskbar, with numbers beginning at 1, representing the leftmost item on the taskbar.
Taking my current taskbar as an example
WinKey + 4 would switch to the folder I have open
WinKey + 5 would switch to the Chrome browser window I have open and WinKey+6 would switch to Spotify.
You may have noticed that there are also items pinned to my taskbar, but not open. Pressing WinKey and the corresponding number would also launch these, so:
WinKey + 1 would launch PowerShell
WinKey + 2 would launch PowerShell ISE
WinKey + 3 would launch KeePass.