If you're looking for maximum fire and brilliance, than a princess cut is a good choice for you. You may like the square shape of a square emerald cut or asscher cut, but it doesn't have enough sparkle for you or you're not crazy about the step faceting, then consider a princess cut. It has a nice, square shape. The only thing is it has very sharp, pointed corners, so you have to make sure your setting protects those 4 points.
The princess cut works well in several different settings. It would look great in a 3-stone ring with 2 princess cuts on either side, or set like so. This is basically a solitaire setting, but with channel-set radiants down the side that graduate leading up to the center stone. It's a really pretty look because all of these stones are mixed-cuts. So if you're looking for something a little bit more contemporary and different, go for a princess cut. It has extreme brilliance and sparkle.