Update! Click here (20 Brush and Painting Tool Shortcuts in Photoshop CC) to see twenty of my favorite tips related to brushes and painting in Photoshop CC in a single post.
‘<’ or ‘>’ moves to the “previous” or “next” brush in the list on the Brushes Panel. Shift + ‘<’ or ‘>’ goes to the first or last brush in list. (At first glance these shortcuts may appear to be making the brush larger and smaller, but that would be because you’re moving from a smaller to larger brush (or vice-versa) in the Brushes panel).