When MSN Messenger was popular the function I used the most was painting directly into your chat.
It was a very comfort and easy way to explain something fast or just for a good laugh.
But nowadays I use a lot of Whatsapp, but there is no real function to directly draw something (yes, paint anything and share it through Whatsapp, but not while chatting).
So I created Paint for Whatsapp. Try it if you were looking for something simular. It's completely free.