What it does
Head Smash is a Rock-type physical move with extremely high Base Power, 80% accuracy, and a steep recoil clause: you take damage equal to half of what you dealt. Hit for 200 HP, take 100 back. That's a punishing self-cost compared to most recoil moves.
That penalty is the reason you want to hit exactly once per target — maybe twice at most. The move exists to blow something up in a single strike, not to trade over multiple turns. Against Flying and Fire types that Rock already hits for double damage, Head Smash often achieves a one-shot even through reasonable bulk.
80% accuracy is meaningful at this damage level. A miss doesn't just waste the turn — you avoided the recoil, which is nice, but you gave the opponent a free turn. Keep track of how many times your user can realistically fire this before recoil takes them out.
Who runs it
Tyrantrum runs it at 72%. Rock/Dragon typing with sky-high physical Attack — Head Smash is the move that makes opponents respect Tyrantrum's presence. Note that Tyrantrum's hidden ability is Rock Head, which removes all recoil — if running the hidden ability, Head Smash can be clicked freely without HP tracking. Without Rock Head, budget your HP carefully before each use.
Rampardos at 41%. Among non-Mega Pokémon, Rampardos sits near the top for raw Attack. Head Smash in Rampardos's hands hits hard enough to KO most targets before recoil becomes catastrophic — the damage is fast enough to outpace the self-damage.
Aggron at 29%, with the Mega form adding substantial Attack boost — Head Smash scales up accordingly. Steelix sees occasional use as a Rock coverage option.
How to use it
In doubles, identify a frail Flying or Fire target and hit it. The goal is a KO in one, maybe two shots — not extended trading. A partner who lowers the target's Defense beforehand (via Intimidate or a move) reduces the hits needed, which directly reduces total recoil taken.
If your user's HP is low enough that the incoming recoil would knock them out, don't throw the move. The recoil triggers on the same turn as the hit — the user can KO the opponent and then faint from recoil in the same action, which counts as a win but leaves you down a Pokémon.
Tips & strategy
Head Smash is a nuke, not a sustained damage tool. Every time you click it you're trading HP for damage, so click it only when you're KO'ing or dealing a large chunk. If there's no frail Rock-weak target, leave the move alone and use something with better accuracy and no recoil cost.
In doubles, if the primary targets aren't Rock-weak, Head Smash sits largely unused. Build the team knowing when and against what you'll press this button.