Here is my Bulky, Lead Gyara:
Gyarados (M) @ Leftovers
EVs: 152 HP / 176 Atk / 36 Def / 144 Spd
Adamant Nature (+Atk, -SAtk)
- Dragon Dance
Sets up with D-Dance, Taunts other leads trying to stealth rock, etc. Taunt can sometimes force a switch, allowing for a free Dance. EQ and Waterfall are decent coverage, EQ has a five type coverage and hits both of Gyara's weaknesses (Rock, Electric) for SE damage, while Waterfall is Physical Stab and has a semi-useless flinch chance.
EVs are a neat distribution, the HP and defensive EVs are an add to bulkyness and work with Intimidate, Atk and Speed allow for an easy sweep of an unprepared team. This set can easily sweep an entire team 6-0 if allowed to set up, and it isn't easily KO'd, usually absorbing 2-3 successive attacks, this is hard to do against something with as much offensive ability as Gyarados.