Piplup

Since the beginning of DPP, Piplup has maintained a niche all its own in Little Cup: being the only pure Water-type with access to Stealth Rock. That's a pretty big boon for Piplup as it means it, a Pokemon with workable defenses and only two weaknesses, can set up the most dangerous entry hazard in the entire metagame. However, that's really the only thing Piplup has going for it. Piplup has a low Speed stat, which means getting up Stealth Rock will be a challenge for it no matter what. Don't expect a lot out of Piplup, because you probably won't be getting what you want out of it if you do.