Well, each of them have up and downs. Personally I like this one build for Hitmonchan which has helped me in a quite a few hard battles in both showdown and in my Ultra Sun game.
Hitmonchan (M) @ Life Orb
Trait: Iron Fist
EVs: 8 HP / 252 Atk / 248 Spd
Jolly Nature (+Spd, -SAtk)
- Drain Punch
- ThunderPunch
- Ice Punch
- Fire Punch
Drain Punch for counteracting the Life Orb, and the rest for coverage. I've used other sets for Hitmonchan but this is my personal favorite for pure damage/coverage.
or
Hitmonchan (M) @ Choice Scarf
Trait: Iron Fist
EVs: 8 HP / 248 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Drain Punch
- ThunderPunch
- Ice Punch
- Fire Punch
If you're a bit riskier. That's what I got...