I'm doing a few things. For one, I'm trying to get the perfect Ultimate PC Box in Platinum, which I do instead of just filling in the pages of the Pokedex for every game, which for those of you who don't know, means filling in every slot in the PC in numerical order with every evolution. I currently have every Kanto except Mew, most of every Johto exept the trio dogs celebi and ho-oh, and every hoenn besides deoxys and jirachi. I'm doing this for many obvious reasons, but the biggest one is to eventually transfer them all to a Unova game, and then my Pokemon Y game. And since I have every Kalos Pokemon except the newest legends and Xiernias, I'm pretty close.
On the other hand, I'm playing my second attempt at Leaf Green Nuzlocke, and I just entered Rock Tunnel, so that's scary >.>