Three Brushes I recently used and felt like sharing:
Snowflake (Or dandelion?):
As long as you keep drawing in more or less straight lines, this one will create bundles of fluffy... things behind the cursor.
Depending on pressure this should makes a pattern like autumn leafs in a storm.
The actual drawing shapes follow the cursor in half circles. Had the idea when visiting the "upcoming features" page.
If you keep the cursor around one point, you can create perfect circles with this one. If you do it better than me in the example picture