Blue Orb Ferrothorn? Hmmm...

Ferrothorn @ Blue Orb
Ability: Iron Barbs->Primordial Sea
Stats: 74/144/131/84/136/20
EVs: 252 HP/252 Atk/4 Def
IVs: 0 Spd can be run for Trick Room
Brave Nature
-Power Whip
-Leech Seed
-Thunder Wave/Iron Head/Poison Jab/Curse
-Spikes/Stealth Rock/Toxic/Swords Dance
With its Fire weakness removed, this Ferrothorn has only Fighting attacks to fear, which its high defenses can easily withstand. Power Whip is the obligatory Grass STAB, and off 144 attack, it
hurts, not to mention the fact that it hits Fighting types neutrally. Leech Seed provides recovery, of course, which is at a premium due to the absence of healing items. For the remaining two slots, as usual, there are options. You can opt to spread status with Thunder Wave and/or Toxic, set hazards that may not necessarily be Defogged or spun away, or run an offensive set using Swords Dance and Iron Head for boosting and secondary STAB, respectively--just be sure to set up Trick Room before you bring it in. (It also gets Curse, which under Trick Room will do you wonders, making you stronger, bulkier, and "faster".)
Of particular note is that this Ferrothorn can actually beat Slowbronite Blissey at its job, not only defeating it one-on-one--
252+ Atk Ferrothorn Power Whip vs. 4 HP / 252+ Def Blissey: 193-228 (29.6 - 34.9%) -- 12.5% chance to 3HKO
252 SpA Blissey Shadow Ball vs. 252 HP / 0 SpD Ferrothorn: 58-69 (16.4 - 19.6%) -- possible 6HKO
--but also having comparable bulk on both sides if Blissey is fully invested in Defense. The two can easily be used alongside each other, as Blissey is a special attacker and has a much better movepool to work with (and can still Wish pass!), while Ferrothorn can wallbreak with Power Whip. As they share a weakness, it is obviously advisable to have a means of dealing with Fighting types or anything carrying Focus Blast.