Tony Shark (Garchomp) @ Rocky Helmet
Ability: Rough Skin
EVs: 252 HP / 4 SpD / 252 Spe
Jolly / Adamant Nature
- Earthquake
- Iron Head / Iron Tail
- Scale Shot / Outrage / Dragon Claw / Dual Chop
- Swords Dance
Earthquake is your most spammable STAB. Iron Head for 100% accuracy and a flinch chance, works well with Chomp's good speed tier, also covers Togekiss, Garchomp's best answer. Iron Tail has lower accuracy, but higher BP and a chance to drop Defense. Scale Shot lets it boost Speed and is multi-hit, although you're sacrificing some of Chomp's defensive utility. Outrage is brutal STAB, but you get locked onto it for 3 turns, which lets Steel types set up in its face. Dragon Claw is more spammable than Outrage but less powerful. Dual Chop is on the same level of power as Claw but 10% less accuracy and hits twice so it breaks Substitutes and sashes. Swords Dance is mandatory to make up for the lack of attack EVs. The reason why I invested into bulk was to set up Swords Dance more safely.
Garchomp-Mega @ Garchompite
Ability: Rough Skin
EVs: 252 HP / 248 Atk / 8 SpA
Brave / Quiet Nature
- Dragon Claw / Outrage
- Earthquake
- Fire Blast
- Swords Dance / Iron Tail
Dragon Claw or Outrage are STAB. One is spammable but weaker, other one is stronger but riskier. Earthquake is, again, your most spammable STAB. Fire Blast melts Ground-resistant steels like Ferrothorn, Skarmory, and Scizor. Coverage vs. Ice types. Swords Dance to overkill (if you're going SD Quiet nature is preferred), while Iron Tail is Fairy coverage.
*P.S. Mega Garchomp works well w/ Tyranitar as a teammate. It should be noted that Mega Garchomp+Tyranitar excels at taking down stall or balance teams that have Blissey, Toxapex, Steels, and Clefable.