What it does
Mach Punch is a Fighting-type physical move with +1 priority — it moves before standard moves in the same turn, as long as the opponent isn't using the same or higher priority. The base power is low, but the point of priority moves isn't damage efficiency per turn, it's sequence control.
In doubles, priority is less universally needed than in singles — you have two Pokémon on the field, so your faster partner can handle urgent threats while the slower one supports. Mach Punch becomes most valuable in a specific scenario: your Pokémon can't win the speed race with a standard move, but it needs to move first to KO a weakened target before it acts. If the opponent is at low HP and a Mach Punch would finish it, that's the play — you skip the speed check entirely.
Contrast with Fake Out: Fake Out causes flinch but works only on switch-in. Mach Punch can be used every turn and is pure damage. The relevant parallel is Bullet Punch — also +1 priority physical contact — but Steel-type rather than Fighting. Conkeldurr and Crabominable both get STAB on Mach Punch, making their version hit notably harder than a neutral-type user would.
Who runs it
Conkeldurr (80% usage) runs Mach Punch because its base 45 Speed means almost everything moves first. This is its only consistent way to get priority output on the board. High base Attack makes even the low-power Mach Punch output meaningful. When paired with Guts or Iron Fist, the actual damage it deals through Mach Punch is higher than the move's base power suggests — Iron Fist boosts punching moves, and Mach Punch qualifies.
Crabominable (56% usage) operates on the same logic — base 43 Speed — with the added angle that it packs Ice typing alongside Fighting, giving it Dragon coverage. Mach Punch serves the same function: priority safety net for a Pokémon that otherwise moves last.
How to use it
The core targeting question is simple: can Mach Punch KO this target? If yes, and a standard move wouldn't because you'd lose the speed race, click Mach Punch. If the target is healthy and you're not winning a KO this turn anyway, use your higher-power move and deal with speed via other means.
Pairing with Helping Hand from a partner gives Mach Punch the extra power kick to secure KOs it otherwise couldn't reach. That combo requires prediction though — you need to correctly identify the target and commit a turn of Helping Hand to it.
Tips & strategy
Within the same +1 priority tier, Speed still decides who goes first. Conkeldurr at 45 Speed is near the bottom of that bracket. Against opponents using their own +1 priority moves, Conkeldurr may actually lose the priority-within-priority speed check.
Contact move recoil from Rocky Helmet or Rough Skin is minor against a bulky Conkeldurr but relevant for Crabominable at low HP — if you're using Mach Punch specifically because you're in a fragile position, that chip could matter.
Against Protect or Detect, Mach Punch is blocked normally — priority doesn't bypass protection. In doubles, if you expect the target to Protect, having your other Pokémon apply pressure elsewhere is the right call rather than wasting the priority move.