Eviolite Porygon2 for sure.
-Eviolite makes it SO. GOSHDARN. BULKY. It's basically got 85/135/135 defenses with Eviolite, and when coupled with a good Special Attack stat, it can deal massive damage while taking very little itself. And, of course, it gets Recover.
-It can spread status like no tomorrow. Access to Tri Attack, Thunder Wave, and Toxic helps it to stall immensely.
-It gets the ability Trace. If you can trace something awesome, like Protean Greninja or Multiscale Dragonite, you're set. You can also run Download for a possible SpA boost right off the bat.
OVERALL: A wall with good offensive capabilities.
-Really high Special Attack. Hits like a truck, especially because of the next reason-
-Its ability, Adaptability. It boosts your Tri Attack (what other Normal STAB would you run) to godly levels. And with the power to burn, freeze, or paralyze, it can be deadly... If you're lucky.
-Decently high speed. This thing is deadly with a Choice Scarf.
-Wide movepool. With stuff like Agility, Nasty Plot, Dark Pulse, Ice Beam, and more, there are a lot of sets you can run.
OVERALL: A powerful Pokemon with not much bulk, but a lot of power and decent Speed.
I prefer Porygon2 just because Porygon-Z dies so quickly. One Close Combat, and it's gone. And let's be honest: in this age of Megas rampaging all over, base 135 SpA is nowhere near what it used to be. So I suggest Porygon2 with Eviolite.