When the Ralts line was first introduced in Gen III, I remember not being terribly impressed with them. When I saw it's new split evolution in Platinum, however, I quickly changed my attitude.
Like many other Pokemon that I like, Gallade received a Mega evolution when ORAS was released. Unlike some of the others I've mentioned on this list (Aggron and Scizor), Gallade's is actually pretty sweet.
With the gladiator look and combat style, combined with an eloquent and gentlemanly air, Gallade is one of the most truly creative Pokemon, and one of my absolute favorites to use!