Prinplup (M) @ Eviolite
Trait: Torrent
EVs: 248 HP / 252 Def / 8 SDef
Bold Nature (+Def, -Atk)
- Stealth Rock/Ice Beam
- Defog
- Scald
- Toxic
Prinplup is actually different from a lower-tier Empoleon in quite a few ways. Primarily, Empoleon's typing, Steel/Water, gives it a lot of resistances, as well as an immunity, and is much more suited for specially defensive sets. Prinplup, however, is only a water type; although this leaves it weaker to Poison, Grass, and Normal, Prinplup can wall Fighting- and Ground-types such as Sandslash. Prinplup is one of the only good defoggers in the tier, and although its bulk isn't anything fantastic, access to defog in NU is very important. Prinplup is similar to a Lumineon that can take repeated hits, and set up stealth rocks. If you have another stealth rock setter, or think defog + stealth rock is too redundant, you can run ice beam for coverage on grass- and dragon-types. Scald is primary STAB, with a nice 30% burn chance, and toxic is to cripple walls like Seismitoad.
Also, I think Ferroseed should be added to the list with a specially defensive set. Ferroseed's unique typing lets it run both physically and specially defensive sets, but the specially defensive set is nicer for completely shutting down Mesprit, Accelgor, Sammurott, HP Fire Vileplume, Gorebyss, Cryogonal, Mismagius, Vivillion, Ludicolo, and Lilligant.