For my Metagross I run an Assault Vest set with Zen Headbutt, Meteor Mash, Bullet Punch, and Earthquake. My Hydreigon is Modest and runs Draco Meteor, Dark Pulse, Flamethrower, and U-Turn (U-Turn is used for momentum rather than damage), but for its item I can't decide whether to run a Choice Scarf to help its speed or a Life Orb to let it switch moves.
My Rotom-W is Modest and is mostly EV'd in HP and Speed (with 56 Special Attack EVs) and runs Volt Switch, Hydro Pump, Will-O-Wisp and Thunderbolt (I couldn't be bothered to breed one with a good Hidden Power) while holding Leftovers. My Talonflame holds a Sharp Beak and runs Brave Bird, Flare Blitz, and U-Turn, pretty standard, but the fourth move is Tailwind instead of something like Swords Dance or Roost to give my team a quick speed boost if it's about to faint.
I actually have a Mandibuzz I bred, and I like the sound of Tyranitar, but I'm wary of putting too many Dark types on a team that already has Hydreigon. What about Mega-Blastoise instead of Mandibuzz? I don't have a Mega on my team, and Blastoise could remove hazards with Rapid Spin while defeating most spin blockers with Dark Pulse. My team would be a little weak to Grass types with Rotom, Blastoise, and Tyrannitar, but Grass isn't that common and the rest of the team resists it.