Found a combo I call "reactive armour"
With: Contrary + Weak Armour, you get +Def, -Spe on every hit; meaning every time you get hit you become more physically defensive and harder to kill.
Given that Contrary as held ability was preemptively banned for some reason (I don't think it'd be that OP in this meta; but I guess it might be); there are very few LEGAL combos to run this. This bums me out a bit, because of the other way around (the Weak Armour mons getting added Contrary) are much more "hidden gem" pokemon that are usually bad and might be viable with the boost. I'll post about both anyways:
Legal:
Serperior @ Skull Fossil
Ability: Contrary + Weak Armour
EVs: 252 HP / 252 Def / 4 SpA
Bold Nature
- Leaf Storm
- Giga Drain/Synthesis
- Glare/Synthesis
- Leech Seed/HP Fire/HP Ice/Light Screen
Physically defensive Serperior, gets slower, but bulkier on every hit, uses Giga Drain and/or Synthesis for recovery. (Can also forget about SpA and run a sub-seeder set. It has decent (not amazing) bulk that becomes great Physical bulk once the ability activates. (75/95/95).
The only other Contrary mon with reliable recovery is Spinda but Spinda's stats are too low to run. Similar Malamar and Shuckle could run the combo, but are unable to be truly bulky due to lack of recovery. Shuckle MIGHT be usable with one of these two sets:
Shuckle @ Skull Fossil
Ability: Contrary + Weak Armour
EVs: 252 HP / 252 SpD / 4 Def
Calm Nature
- Rest
- Shell Smash
- Infestation
- Toxic
(Normal Contrary Shuckle boosted by extra Def boost)
Shuckle @ Skull Fossil
Ability: Contrary + Weak Armour
EVs: 252 HP / 252 SpD / 4 Atk
Sassy Nature
- Power Split
- Gyro Ball
- Rest
- Knock Off
(Attempts to steal Physical Atk prowess from the first attacker out, uses the extra spe malus for max gyro ball power).
-Neither is that good though honestly.-
Illegal:
Only posting because I put so much thought into it already; Contrary is on the list of preemptive bans, probably more because of V-Create Victini or Draco Meteor Latios than this gems in the rough, but "simple bans" throw out the baby with the bathwater for the sake of simplicity.
Magcargo @ Dark Gem
Ability: Weak Armour + Contrary
EVs: 252 HP / 252 SpD / 4 SpA
Calm Nature
- Overheat
- Recover
- Earth Power/HP Rock
- Stealth Rock/Will-o-Wisp/Shell Smash
Magcargo's already good Def gets boosted every hit, thus investing in the lower SpD is a better call. Can use Shell Smash (Which will lower your SpA, which can be risen again by your STAB) or Sand Storm to boost SpD. Only normal Rock STAB available (Ancientpower) is same power as HP and a bad call because of chance of lowering all stats.
Mandibuzz @ Dark Gem
Ability: Weak Armour + Contrary
EVs: 252 HP / 252 SpD / 4 Atk
Careful Nature
- Roost
- Foul Play
- Toxic
- Knock Off/Brave Bird
Kabutops @ Dark Gem
Ability: Weak Armour + Contrary
EVs: 252 HP / 252 Atk / 4 Def
Adamant Nature
- Superpower
- Rapid Spin/Waterfall
- Aqua Jet
- Stone Edge
Skarmory @ Dark Gem
Ability: Weak Armour + Contrary
EVs: 252 HP / 252 SpD / 4 Def
Sassy Nature
- Roost
- Stealth Rock/Spikes
- Brave Bird/Iron Head/Spikes
- Whirlwind
-Skarm is probably the best illegal user, as it takes it's already amazing physical bulk and turns it overwhelming.
Other users if Contrary was ever unlocked (currently illegal):
Crustle, Garbodor, Omastar, Onix, Vanilluxe