I was playing around with my Wacom tablet tonight, made a new brush in Acorn, and drew the little guy above. I called the preset "Dart", and you can download it from here: Dart.acbrush.

If you're running Acorn 2 or layer, you can double click that file and Acorn will ask to install it for you. It will then be moved to your ~/Library/Application Support/Acorn/Brushes/ folder.