Emoji For Hangouts is a Chrome extension designed to make it easier to use emoji in Google Hangouts. It is made to be as simple and uninstrusive as possible, with no GUI. Instead, you can just type Discord-style emoji codes. For example:
:thinking: -> 🤔
:hamburger: -> 🍔
:cowboy: -> 🤠
There is also tab completion if you have typed a partial emoji name. Repeatedly pressing tab cycles through the possibilities, sorted by frequency of use.
Download it on the Chrome Web Store!
Note: Make sure to reload your Gmail/Hangouts pages after installation.