As someone with large lids and a deep crease, my favorite eye brushes are quite big and wide as to not create harsh lines and edges. But sometimes there's a need for a more precision in the crease or lid, especially when applying very pigmented dark colors to the outer corner. This is where Nars #12 Small Domed brush comes into play.
The unique thing about Nars #12 is that unlike many small brushes for detailed work it is fluffy and not very dense, so it won't pick too much color. The small dome fits into small spaces (which is why this brush is usually a top pick for Asian eyes) and deposits the right amount of dark color where you need it. The fluffiness makes it ideal for blending, and since it's small enough, the color will stay in the right place and won't spread too far.
Less pigmented colors and dramatic contrasts require a denser brush, but for certain colors and looks this is the best brush I've come across.
Nars Small Domed Eye Brush #12 ($27) is available from narscosmetics.com.
All photos by me with the help of Sophie and Giselle.