Real Techniques - shading brush. Not only you can use it for shading, but I find it very useful for creating an outter V. Before that, I had never managed to create a precise one. This brush is amazing.
Real Techniques Shading Brush. I ADORE this brush. It's perfect for packing on lots of shadow in a small space. I typically use it to sort of smoke out my liner a bit and create a shadowed winged effect.