I know it's kind of late but I wanted to share this core I came up with.
My team was in need of a Wide Guard user, but the problem with Hitmontop is that it has too many things it wants to run (Wide Guard, Quick Guard, Close Combat, Feint, Mach Punch, Sucker Punch, ...) but only four things that it can. It's also pretty easy to take down with single target attacks as well. So I started to use this set:
Probopass @ Rocky Helmet
Ability: Magnet Pull
EVs: 252 HP / 252 SpA / 4 SpD
Modest Nature
IVs: 0 Atk
-Thunder Wave
-Wide Guard
-Earth Power
-Flash Cannon
Alongside Thunder Wave, it beats a lot of stuff easily with Flash Cannon and Earth Power, including the common Weavile and some Arcanine. The one issue was that it lost easily to some single-target attacks such as Close Combat (and to a lesser extent Earth Power), which was made worse by its lack of Protect. To fix this, I decided to add:
Togekiss @ Babiri Berry
Ability: Serene Grace
EVs: 244 HP / 252 SpA / 12 SpD
Modest Nature
IVs: 0 Atk
-Air Slash
-Heat Wave
-Protect
-Follow Me
This Pokémon takes attacks aimed at Probopass with ease, such as Close Combat, Earth Power, and to a lesser extent Scald. Wide Guard protects it against many common spread moves such as Blizzard, Rock Slide, and maybe Discharge. I chose to use a Babiri Berry to more easily beat Scizor, which is relatively unhindered by Thunder Wave and walls Probopass otherwise. The reason I used Protect on this set is so Probopass can paralyze a threat (read: anything that can be paralyzed), such as Suicune or Ludicolo, while Togekiss proceeds to flinch-spam it.
I haven't really worked on the EVs for either, though.
Replay:
http://replay.pokemonshowdown.com/sinnohclassic-403575102