Tussle, ruckus and kerfuffle.

If you don't mind being slower than most things, Octillery is an unconventional choice that might be worth your time. Its attack stats are solid for in-game play (105/105 is stronger than most things), and it gets a myriad of attacks to abuse, like Fire Blast, Ice Beam (which it learns naturally), Surf, and Gunk Shot. In theory, it seems like a solid Pokemon for in-game play, though I've never actually tried it. If it appeals to you, though, I would recommend it. If not, I like Vaporeon as my designated Water-type. 110 base Special Attack trumps Octillery's, though Vap's movepool is shallow in comparison to the octopus. Surf / Shadow Ball / Ice Beam, Aurora Beam, or Blizzard is almost always enough for you, though. I was lucky enough to have one with Hidden Power Electric for its fourth move, but if you aren't that fortunate, you could try something like Toxic or Acid Armor, I suppose.

Claydol.

whole team of Bidoof.

Lickylicky, Froslass and Porygon-Z

I second lickilicky.

@Scheisskopf; I've had a few people suggest Octillery to me, so I probably should give it a shot since it seems to be a popular suggestion.
@Mijzelffan; I looked mister, and Claydol isn't in the Plat dex. Also no to Licklicky >:I
@yourlilemogirl; NO >:(
@PkmnGreen; No to Lickilick >:I Maybe to Froslass and Porygon-Z though. I heard good things about Porygon-Z but I never tried one. Would you recommend Download or Adaptability for it?

@Mijzelffan; I looked mister, and Claydol isn't in the Plat dex.

You used a medicham in your White team, so don't give me this "it's not in the dex" crap.

@Zeb;

@yourlilemogirl; NO >:(

you wanna fight m8. i'll take you. I'll take you beyond the stars and into a nightmare.

@Zeb; Download definitely, and make sure it has Tri-Attack, it's amazing :I

Hyper Beam is also really nice in-game, since you get to switch for free after killing something anyway. A great starting move for your Porygon.