Lagging Tail

Makes the holder move last in its priority bracket. (Hold)

Lagging Tail forces your Pokémon to move last within its priority bracket. This sounds bad, but it's useful for moves like Gyro Ball (which deals more damage when you're slower) or Trick Room strategies.

You can also Trick this item onto a fast opponent to cripple their Speed advantage. It's a niche item, but when it fits the strategy, it's surprisingly effective. Kind of the opposite of Choice Scarf, if you think about it!