Quagsire( Analysis 4 sets)

Set 1 Unaware Stockpile
Quagsire (M) @ Leftovers
Trait: Unaware
EVs: 252 HP / 124 Def / 132 SDef
Careful Nature (+SDef, -SAtk)
- Recover
- Stockpile
- Toxic/Safeguard
- Waterfall/Earthquake
This thing is a MONSTER, after 3 Stockpiles all his Defences are above the 400.
BAcked up by Recover and Toxic no one will be able to do anything,yay.
You can then use Waterfall to chip away HP little by little.
Safeguard can be used for Protection to Status instead of Toxic

Set 2 Amnesia
Quagsire (M) @ Leftovers
Trait: Unaware
EVs: 252 HP / 252 Def / 4 SDef
Relaxed Nature (+Def, -Spd)
- Amnesia
- Encore/Yawn
- Recover
- Waterfall
Fairly easy to use, just make sure to get in a Amnesia.
Encore is this sets best trick even with the nerf, even tough Yawn could work better.
Just depends, what you like to use more.
Waterfall is just for a Stab and to avoid being shut down by Taunt.
Earthquake is a stronger move but flying types screw you over then.

Set3 Curse
Curse Quagsire isnt much seen anymore but still deserves a Mention.

Quagsire (M) @ Leftovers
Trait: Unaware
EVs: 252 HP / 40 Def / 216 SDef
Careful Nature (+SDef, -SAtk)
- Curse
- Stockpile
- Recover
- Waterfall
This set is SICK. When used right Stockpile and Curse become a immense combination that can kill and wall half of the current Metagame(still Serperior is a bitch to fase).
Recover is a great move for when the HP is down cuz well yeah, HP.
Waterfall after a few times Curse hits quite hard.

Set 4 SubPunch

Quagsire (M) @ Leftovers
Trait: Water Absorb
EVs: 252 HP / 216 Atk / 40 SDef
Adamant Nature (+Atk, -SAtk)
- Substitute
- Focus Punch
- Earthquake
- Waterfall

Unexpected sets are always fun, and can tear trough teams with ease.
A SubPunch set seems lolzy and it is.
Even tough it throws your opponent very hard of guard it is still inferior to the other 3 sets.
If you need a pokemon with good HP and a fun set, use this set.
Sub when someone Switch and use Focus Punch then.
Waterfall and Earthquake are just fillers as they hit the ghosts.
To bad Unaware and Focus Punch can't be used..