Within Teamwork Chat if you type ":" into the message field, you'll find a list of suggestions. This list will update as you type more characters. For example try typing ":b".
To find a full list of the emojis we support, here's a link to our cheat sheet.
Besides the ones listed in the cheat sheet, we also support the old school short emojis too, like :) or :(.
For more information see: Markdown in Teamwork Chat