I spent years of using regular silverware and having my brownies fall apart and stick to the knives.  This always resulted in a sloppy looking dessert plate.  I'm am not a great baker, but brownies are one of the things that I make well.  I wanted them to appear as good as they tasted.  After some trial and error, I discovered that the best knife to use is a plastic knife.  Brownies almost never stick to the plastic knife.  This allows you to create tidy little square browines.