Zoroark

Zoroark is a very popular Pokemon from Generation 5, and it's translated reasonably well into Pokemon Go. While frail, its Dark Type DPS is decent, meaning it's not the worst option if you need some Dark coverage, though the continued dominance of Ghost Types in general makes this option a bit dubious.

Worth noting is that Zoroark has a signature Dark Type move called Night Daze in the main series, so the future may be even brighter for this trickster.

Best PvE Offensive Moveset

• Snarl and Foul Play make for Zoroark's best possible moveset.
• Shadow Claw is semi-close to Snarl and hits the same types for Super Effective damage, but it's ultimately an inferior move due to a lack of STAB.
• Sludge Bomb and Flamethrower are lesser options.

Best PvE Defensive Moveset

• Snarl is, once again, the move of choice, though Shadow Claw can still have a bit of use.
• Sludge Bomb hits harder and has counter-coverage but is hard-walled by several big name attackers, while Flamethrower can flatten some common attackers with Super Effective damage. 
• Foul Play is solid, but it matches Snarl's type, so it's best matched with Shadow Claw despite the two having a similar effectiveness profile.

Shadow Claw is one of the best Fast Moves in the game, and boasts good damage output and energy gains. Snarl falls behind in damage output despite benefiting from STAB, and narrowly offers slightly higher energy generation. 

Foul Play is the main Charge Move due to STAB and lesser energy costs compared to other options. Sludge Bomb is recommended for its coverage against Fairy-type Pokemon, though Zoroark's fragility will likely cause it to lose to Charm before it can use Sludge Bomb. Flamethrower alternatively has a niche against Zoroark's weakness to Bug-type Pokemon.