Within Teamwork Chat, you can use emojis in your messages to other users.
To add an emoji, you can use the emoji picker located to the right of the message field.
Alternatively, you can type : into the message field, you will see a list of emoji suggestions. This list will update as you type more characters, for example :s.
You can find a full list of supported emojis on this cheat sheet.
As well as those listed on the cheat sheet, traditional short emojis such as :) and :( are also supported.
For more information see: Using Markdown in Messages