What it does
Overcoat does three things: immunity to sandstorm and hail chip damage, immunity to powder moves (Sleep Powder, Spore, Stun Spore), and immunity to Rage Powder redirection.
That third one is the one that catches people off guard. Amoonguss is one of the most common doubles support Pokémon — its whole gameplan is redirecting attacks with Rage Powder while threatening Spore. An Overcoat carrier ignores both. The redirect doesn't work on it, and Spore fails outright. You can click an attack straight at the real threat without a mushroom in the way.
Sand immunity matters in specific team matchups too. Against sand teams, every turn your Overcoat Pokémon doesn't lose 1/16 HP is a turn it survives into endgame where chip totals decide who wins.
Who runs it
Kommo-o (27%): Dragon/Fighting, and its other ability is Bulletproof — which blocks ball and bomb moves. The 27% Overcoat number says that a meaningful portion of Kommo-o users are trading Bulletproof coverage for sand immunity plus Rage Powder/Spore immunity. Whether that's correct depends entirely on what you expect to see.
Reuniclus (14%): Pure Psychic, base 30 Speed, primary role is setting Trick Room and then attacking slowly under it. Overcoat keeps it alive through Sleep Powder attempts before Trick Room is up, and shields it from weather chip in sand or hail matchups where every bit of HP matters.
How to use it
Kommo-o line: Run it on sand-adjacent or Amoonguss-heavy matchups. When Amoonguss tries to redirect your Kommo-o into it with Rage Powder, nothing happens — you hit the intended target. When sand ticks, Kommo-o ignores it. This frees up your damage calcs to assume full HP through turns where other team members are getting chipped.
Reuniclus line: Its job is to set Trick Room reliably. The main way this fails is getting put to sleep before Trick Room goes up. Overcoat removes that threat entirely. Pair it with speed-control and let it do its job without interruption.
Tips & strategy
Bulletproof vs. Overcoat on Kommo-o: Bulletproof is the default because ball/bomb moves show up constantly — Sludge Bomb, Flash Cannon, Shadow Ball. If your regional meta runs heavy Amoonguss or sand, Overcoat becomes the better call. Check what's actually popular in your bracket before committing.
The Rage Powder immunity is worth spelling out one more time: in doubles, the most common answer to threatening setup is redirect-plus-Spore from Amoonguss. An Overcoat Pokémon punches straight through that wall. At high-level play, that's genuinely valuable — it's the kind of 'hidden' property that experienced players notice and beginners miss.