Zigzagoon @ Oran Berry
EVs: 196 Atk / 188 Def / 108 SpD
~ Belly Drum
~ Seed Bomb
Belly Drum sweeper set. Smogon analysis:
Zigzagoon only needs one set to sweep, and it's this one. After only one turn of setup, its Attack stat is boosted to a jaw-dropping 52, easily OHKOing every common Pokemon in the tier. Oran Berry allows Zigzagoon to restore any HP lost while setting up, allowing it to always pull off a Belly Drum. From here, ExtremeSpeed will easily clean the opposing team, as not only does it have priority over normal moves, but also priority over most other priority moves. There is room for only one coverage move in Zigzagoon's movepool; Seed Bomb allows it to easily KO bulky Rock- and Ground-types that might try to stop its sweep. It also scores an OHKO on Hippopotas, one of the bulkiest Pokemon in the tier. Protect is used to prevent Fake Out from hitting Zigzagoon, allowing it to continue its sweep unscathed.
The EV spread maximizes Zigzagoon's Attack , while sharing the leftover EVs between Defense and Special Defense. There is no need for Speed investment on this set, as ExtremeSpeed is a priority move, and Zigzagoon is naturally faster than all of Seed Bomb's targets. Pursuit support or a way to eliminate Ghost-types is nearly mandatory, as nearly all of them can outspeed Zigzagoon and easily OHKO it. Magnemite is also appreciated as a teammate, as it has the Magnet Pull ability to trap the Steel-types that might wall Zigzagoon. Magnemite can also weaken Lileep with Flash Cannon, allowing Zigzagoon to KO it later. Pickup is the only option for this set, as ExtremeSpeed is an event-only move released way back in ADV. While essentially useless, Pickup can situationally come in handy to recover an opponent's consumed item for Zigzagoon's use.