If you only own one makeup brush in your life it needs to be the NARS Kabuki Brush (although I do not recommend just owning one makeup brush...talk about roughing it.) This brush makes contouring the easiest thing ever, it literally allows you to get into areas you can't get into with a regular makeup brush and trust me I have a LOT of brushes.
I use it to define my cheekbones, make my nose look smaller (it can never be small enough!) and define my jawbone. This literally makes contouring take 2 seconds so you can look just as fab in the mornings as you do at night.