One of my all time favorite brushes is the Sephora Collection Pro Natural Smudge Brush #11:
I LOVE this brush for getting straight lines when I'm doing the outside 'V' for eyeshadow as well as smudging my eyeliner!
Pro's:
-Good quality
-Dense, soft bristles
-Doesn't shed a lot
Con's:
-I can't really think of any!
You can get this brush at Sephora for $18.