Best new features that do not require Office 365
First up, here are the key features that don't need an Office 365 subscription.
Word, Excel, and PowerPoint 2016: Smart Lookup
The new Smart Lookup feature lets you find facts and such through the Bing search engine. It can see the context of selected text by examining surrounding content and then try to provide relevant results. I usually jump out to a browser to do a search, but I can see how this adjustment might make work a little easier.