Since this is Black 2/White 2...
Water
Azumarill; get a Huge Power Azurill in the Floccesy Ranch. They're hard to train up at first, but you get TM27 Return from Bianca after beating Cheren, and that's the move that enables it to train without having to switch train.
Simipour; not as good as Azumarill in my opinion, but if you don't want to baby an Azurill, then Simipour is another option. It has equal attack and sp. atk, meaning it can make use of moves like Waterfall, Surf, Acrobatics and Ice Punch/ Beam, so it's got a more diverse movepool than Azumarill (but the Huge Power ability makes Azumarill my 1st choice).
Fire
Darmanitan; the normal Darumaka you get in Route 4/ Desert Resort have Hustle, which will turn into Sheer Force when they evolve, meaning a great boost for moves like Flare Blitz, Rock Slide, and even just FIre Punch.
Chandelure; even though you said you wanted higher attack than sp. atk, Chandelure is a really good Pokemon. I think if you have a physical based Water type, a special Fire type would work well with it. I'm also assuming you started with a Snivy, and Serperior works best with Coil & Leaf Blade, so it's a good idea to get a special base Pokemon on your team.
Chandelure's got great typing, incredibly high sp. atk and it can get Shadow Ball & Flamethrower via TM, meaning you can evolve it with a Dusk Stone as soon as it evolves into Lampent.
