Quagsire

Behold, Lord Quagsire! Majestic, glorious, triumphant..... and derpy-looking. Quagsire boasts strong moveset options, but lacks stats to use them well. A relatively high STA stat compared to other Pokemon suggests that Quagsire be a decent gym defender, and with only 1 weakness and a handful of resistances, Quagsire ain't too bad for defense. That double weakness to Grass-type attacks shouldn't be overlooked though, as any attacker can simply switch to a Grass Pokemon and make short work of Lord Quagsire. 

Best PvE Offensive Moveset

• Water Gun has better performance on paper, but its Charged Move type-pairing isn't the best.
• Aqua Tail* isn't the best, but it works with Water Gun.
• Mud Shot isn't far behind and is recommended overall. 
• Earthquake should be chosen for a Ground-type role.
• Stone Edge is a powerful move, but lacks STAB and synergy with Quagsire's moveset.
• Sludge Bomb is also quite strong, but isn't meant for Quagsire. 
• Acid Spray is a PvP move. 

Best PvE Defensive Moveset

• Both Water Gun and Mud Shot are poor moves for defense, but the latter is slightly better.
• Sludge Bomb is the best choice for defense due to being a 2-bar move, as well as coverage against Quagsire's only weakness: Grass-types.
• Aqua Tail* is a great secondary option, though it can leave Quagsire vulnerable to common Water Type counters.
• Stone Edge is slow to access but also hard to dodge. 
• Earthquake is too slow for defense.
• Acid Spray is meant for PvP. 

Mud Shot offers incredible energy gain, allowing Quagsire to consistently make use of its wonderful coverage. It is preferred over Water Gun.

For an inexpensive yet strong Charged Move for baiting shields and harassing, Quagsire appreciates utilizing either Mud Bomb or Aqua Tail, allowing it to deal consistent Ground or Water-type damage. When paired with Stone Edge, Quagsire boasts potentially nearly flawless coverage. Earthquake is a solid move and turns Quagsire into a fearsome closer, but is less preferable to Mud Bomb due to its cost. Sludge Bomb can be used over Stone Edge to surprise Grass-type Pokemon (not named Venusaur or Trevenant), but sacrifices coverage against Flying-type Pokemon. Acid Spray has poor synergy with Mud Shot's low DPT and should be avoided.