Pokemon Sun and Moon's online Battle Spot ladder is full of wild teams. Since all games are best-of-one (unlike live tournaments, which are best-of-three), many players bring gimmicks to steal the win in unexpected ways. Even the best competitive player can be caught off guard, because they never know what to expect.
Take this episode of Aaron Zheng's "Road to Ranked" YouTube series. As one of the game's most veteran and most-decorated players, he's seen a lot of crazy stuff and knows what to look for. But in the first match of the game, with his Snorlax poised to sweep the rest of his opponent's team, Zheng got a surprise (skip to around the 9:30 mark if you don't have 25 minutes to spare!)
On the second to last turn of the game, Porygon2 goes for Protect, a move it is almost never seen using. Zheng immediately recognised it as a weird move, but the gravity of the situation didn't hit him until the opposing Choice Banded Gigalith went for Explosion. At that point, his mouth hung open, speechless.
Zheng knew that might cost him the game. The Choice Band item only allows a Pokemon to use one of its four moves, but that move's damage is boosted by 50 per cent. Considering Explosion already hits everything on the field with 250 base power (most attacks don't even crack 100), the damage potential is even crazier. Then when you factor in Gigalith's 135 base attack stat and almost anything that doesn't resist normal type attacks is going down.
Granted, using such a move required sacrificing the attacking Pokemon, but it easily KO'd Zheng's Persian. Snorlax only survived on 23 HP, and that was only because Zheng had boosted its defence stat earlier in the game with Stockpile. If he hadn't done that, it would have been game over right there. And on top of that, if he hadn't Recycled his Figy Berry, an item that recovers 50 per cent of a Pokemon's health, he could have been in danger of losing his Snorlax to the remaining Porygon2.
While he did manage to win the battle, it can serve as a reminder to always prepare for the unexpected. If Zheng had underestimated his opponent and not taken his time to set up the win properly, it could have cost him the game.