Users would be amazed if you support emojis as Github does e.g. in their commits (see http://www.emoji-cheat-sheet.com). The ability to express emotions in a checkvist line makes editing tons more fun.
Wenliang LU commented
Thanks Jaege. Now I have learned emoji is basically UTF characters. You can just copy and paste them in any text file. but how it displays depends on your system (phone / browser, etc).
asher raz commented
I suggest to add shapes that are easy + shapes like check mark - cancel etc.
Actually, emoji can be used in most text fields of checkvist, you just need to use the HTML-code for the icons. For example: the smile face is 😊 You can just copy the HTML-code from https://unicode-table.com/en/1F60A/ and paste in the text field in checkvist.