- Have a Pokemon such as Lickilicky, Poliwrath, etc. with Belly Drum.
- Have a physical sweeper with Psych Up. Because it's a TM, there are many Pokemon able to abuse this.
Here's how the combo works:
Have the Belly Drummer throw up a Belly Drum, and have its partner use Psych Up to copy the maxed out Attack level. You'll instantly have a devastatingly destructive physical powerhouse in one turn, able to storm the field of anything that gets in its way.
If the HP cut from Belly Drum turns you off, then you can always substitute it for Swords Dance, but that'll take longer to set up, while the Belly Drum set takes but one turn to do.
Gluttony Sitrus berry linoone can abuse this, but a sash works as well.