skribbl - Word guessing based on drawing.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.
LetsDraw.It - Guess and Draw, Drawing Battle, Pictionary, Copy picture - online drawing games where you can compare your skill with others.
Sketcharama - Draw a given word and let the other players guess your sketch.
gartic.io - Draw, guess, and win!
Sketch Toy - A drawing application that lets you save and share replays of your work with friends.