skribbl - Word guessing based on drawing.
Papermind - Papermind Slack App is a collaborative article-editing and document management platform for Slack
LetsDraw.It - Guess and Draw, Drawing Battle, Pictionary, Copy picture - online drawing games where you can compare your skill with others.
Slenke - Project management & team collaboration
gartic.io - Draw, guess, and win!
Trainual + Slack Integration - Capture knowledge or access training right inside Slack