I usually always choose the water starter. Always. So, in DPP, I started with Piplup. But I was very disappointed by it. I guess it's Emploeon's double type, that really disturb me. A water type has to be strong against fire, so I couldn't bear it not to resist that much. So, I reluctantly started a new game (I was far in the game, but the starter is too much important for me), and picked Chimchar. And, I have to say that I'm very happy with my decision. Infernape's way more practical than Empoleon, and it's great for the Battle Frontier.
In HGSS, I chose Totodile. My favourite starter ever. Plus, it's the water type, so it was an easy choice for me.