Time to Analyze!
Zen Headbutt
Zen Headbutt covers Pangoro's Fighting weakness, as well as… Poison? I guess it could be used if your team is full of Fairies, but other than that, it's a poor choice.
Ice Punch
Ice Punch sees a bit more versatility and use than Zen Headbutt, and is probably the move to go with if you pick Iron Fist. It covers Pangoro's Flying weakness (let's face it, Pangoro shouldn't be staying in on anything with a reliable Flying STAB anyways) as well as Dragon, Ground, and Grass. A solid choice.
Stone Edge and Rock Slide
Stone Edge is the move to go for if the ability is Scrappy, being more powerful than Ice Punch. However, you may find yourself missling a lot between it and Gunk Shot. For use in Doubles, pick Rock Slide, as it targets both opponents and has a high flinch rate.
Item
The preferred item for Pangoro is Choice Band, allowing it to hit things fairly hard. If you dislike Choice items, Big Root makes Drain Punch recover more HP.
Ability
Iron Fist is generally superior to Scrappy, boosting Drain Punch and Ice Punch. Scrappy would let you hit Ghosts with Drain Punch, but Crunch already lays low and Ghost Pangoro is fighting.
Conclusion
Your Pangoro would function best with this set:
Pangoro@ Choice Band
Ability: Iron Fist
Nature: Adamant
EVs: 252 Atk / 252 HP / 4 SDef
- Drain Punch
- Crunch
- Gunk Shot
- Ice Punch/Rock Slide
Use Ice Punch for Singles and Rock Slide for Doubles. Also, don't stay in on Fairies, as Pangoro isn't surviving any Fairy attack. Use Gunk Shot when a Fairy is likely to switch in.