Greninja, ye say?
Heracross @ Choice Scarf
Adamant, 252 Atk, 4 Def, 252 Speed
Ability: Guts
- Megahorn
- Knock Off
- Stone Edge
- Close Combat
Scarf Hera gives you something fast (which everything so far very sorely lacks) to revenge kill, and generally smash into anything you need dead or weakened.
Megahorn rips into Cresselia (which we can hardly tickle with the above 5), Hydreigon, and Ludicolo. Knock Off is outright obnoxious and removes items from defensive and offensive threats alike, and also murders almost any form of Gengar, Mega or not. Stone Edge is generally coverage, but nails Thundy, Zapdos, Salamence, and Charizard pretty hard. Close Combat is accurate, powerful STAB for crushing Khan, Heatran, Infernape, etc.
Against Greninja, the LO sets are simply outsped and OHKO'd, against Sash, only the rare Extrasensory will KO Heracross (HP Fire will not KO with Sash), and with Talonflame comfortably handled by Rotom-H and Mence, Hera should be adequately covered by the above 5. Also acts as a status switchin, so that Mence doesn't have to eat a WoW or Toxic. Rotom-H sponges T-Wave from the vast majority of common users.
EVs are obvious, 4 Def reduces the odds of Psyshock from a few specific Psychic mons from KOing at full HP, and Adamant + Scarf outruns pretty much anything you'll ever need while Adamant adds much-needed power. Can easily rampage through a team once all resists to CC, Knock Off, or Megahorn are weakened or removed. Thanks to Hera's natural Special bulk, it can also maim a few neutral matchups like Rotom-W as well. Absurdly deadly if it nets a Guts boost but by no means required. From personal use, its pretty good against all Weather matchups: all inducers bar Hippowdon are outpsed and 2HKO'd at worst, along with common abusers like Ludicolo, Venusaur, and Excadrill.
Weavile can switch in but has to mind Scald Burns; LO Greninja can't OHKO without Low Kick. Same with Hera, but LOVES burns, and fears Extrasensory instead. With Sash Greninja, Heracross is in no danger of a 2HKO from Scald, while Weavile has ~56% chance to be 2HKO'd and can't handle a burn. Weavile can Fake Out -> Knock Off / Icicle Crash to avoid a 2HKO from all sets, Hera has to eat 1, maybe 2 hits from a full HP Sash set.