I'm sorry for this double post, but I'd like to share my first idea of a core.
Garchomp @ Garchompite
Sand Veil ( Sand Force )
Rash
160 Atk, 216 SpA, 132 Speed
- Earthquake
- Fire Blast
- Draco Meteor
- Stone Edge
Tyranitar @ Smooth Rock / Leftovers
Sand Stream
Careful / Sassy
252 HP, 60 Atk, 100 SpA, 96 SpD
- Thunder Wave
- Dragon Tail / Roar
- Rock Slide
- Ice Beam / Fire Blast / Pursuit / Thunderbolt
Shuckle @ Binding Band / Leftovers
Sturdy / Contrary
Bold
252 HP, 252 Def, 4 SpD
- Infestation
- Sticky Web
- Toxic / Knock Off
- Protect / Rest / Stealth Rock / Power Split / Shell Smash
I've been trying to find some teammates to help Megachomp play to its strength. On Garchomp, 132 speed EVs outspeeds all unscarved mons under base 123 speed (Greninja) after Sticky Web and Mega Evolving. Here are some offensive calcs made possible with sand support:
216+ SpA Mega Garchomp Fire Blast vs. 252 HP / 0 SpD Skarmory: 326-384 (97.6 - 114.9%) -- 87.5% chance to OHKO
216+ SpA Mega Garchomp Fire Blast vs. 252 HP / 0 SpD Ferrothorn: 428-508 (121.5 - 144.3%) -- guaranteed OHKO
216+ SpA Mega Garchomp Fire Blast vs. 252 HP / 216+ SpD Mega Scizor: 360-428 (104.6 - 124.4%) -- guaranteed OHKO
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 0 SpD Gliscor: 273-322 (77.1 - 90.9%) -- guaranteed 2HKO after Poison Heal
-2 216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 0 SpD Gliscor: 136-162 (38.4 - 45.7%) -- 64.6% chance to 3HKO after Poison Heal
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 0 SpD Hippowdon: 282-333 (67.1 - 79.2%) -- guaranteed 2HKO after Leftovers recovery
-2 216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 0 SpD Hippowdon: 141-166 (33.5 - 39.5%) -- 18.1% chance to 3HKO after Leftovers recovery
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 252+ Def Hippowdon in Sand: 159-187 (37.8 - 44.5%) -- guaranteed 3HKO after Leftovers recovery
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Sylveon in Sand: 349-412 (88.5 - 104.5%) -- 31.3% chance to OHKO
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Mega Venusaur in Sand: 207-244 (56.8 - 67%) -- guaranteed 2HKO after sandstorm damage
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 252+ Def Mega Venusaur in Sand: 153-181 (42 - 49.7%) -- 27.3% chance to 2HKO after sandstorm damage
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 4 SpD Mega Venusaur: 184-217 (50.5 - 59.6%) -- guaranteed 2HKO after sandstorm damage
216+ SpA Mega Garchomp Fire Blast vs. 252 HP / 4 SpD Filter Mega Aggron: 219-258 (63.6 - 75%) -- guaranteed 2HKO
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Filter Mega Aggron in Sand: 177-208 (51.4 - 60.4%) -- guaranteed 2HKO
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Azumarill in Sand: 297-349 (73.5 - 86.3%) -- guaranteed 2HKO after sandstorm damage
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Mega Blastoise in Sand: 211-249 (58.2 - 68.7%) -- guaranteed 2HKO after sandstorm damage
-1 160 Atk Sand Force Mega Garchomp Stone Edge vs. 252 HP / 164+ Def Gyarados in Sand: 202-238 (51.2 - 60.4%) -- guaranteed 2HKO after sandstorm damage
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 4 SpD Mega Tyranitar in Sand: 123-145 (30.4 - 35.8%) -- 45.3% chance to 3HKO
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 252+ Def Mega Tyranitar in Sand: 266-314 (65.8 - 77.7%) -- guaranteed 2HKO
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 252+ Def Eviolite Chansey in Sand: 327-385 (46.4 - 54.6%) -- 98.8% chance to 2HKO after sandstorm damage
160 Atk Sand Force Mega Garchomp Stone Edge vs. 252 HP / 252+ Def Mandibuzz in Sand: 230-272 (54.2 - 64.1%) -- guaranteed 2HKO after Leftovers recovery
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 4 Def Deoxys-D in Sand: 163-193 (53.6 - 63.4%) -- guaranteed 2HKO after sandstorm damage
160 Atk Sand Force Mega Garchomp Earthquake vs. 4 HP / 0 Def Mega Garchomp in Sand: 219-258 (61.1 - 72%) -- guaranteed 2HKO (lol)
160 Atk Sand Force Mega Garchomp Earthquake vs. 56 HP / 0- Def Kyurem-B in Sand: 274-324 (67.6 - 80%) -- guaranteed 2HKO after sandstorm damage and Leftovers recovery
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 0 SpD Rotom-W: 204-240 (67.1 - 78.9%) -- guaranteed 2HKO after sandstorm damage and Leftovers recovery
160 Atk Sand Force Mega Garchomp Stone Edge vs. 252 HP / 252+ Def Rotom-W in Sand: 113-134 (37.1 - 44%) -- guaranteed 3HKO after sandstorm damage and Leftovers recovery
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 4 SpD Landorus-T: 258-304 (67.5 - 79.5%) -- guaranteed 2HKO after Leftovers recovery
-2 216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 4 SpD Landorus-T: 129-153 (33.7 - 40%) -- 28.5% chance to 3HKO after Leftovers recovery
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Manaphy in Sand: 246-291 (60.8 - 72%) -- guaranteed 2HKO after sandstorm damage and Leftovers recovery
160 Atk Sand Force Mega Garchomp Stone Edge vs. 252 HP / 252+ Def Shuckle in Sand: 126-150 (51.6 - 61.4%) -- 95.3% chance to 2HKO after Leftovers recovery
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Conkeldurr in Sand: 258-304 (62.3 - 73.4%) -- guaranteed 2HKO after sandstorm damage
216+ SpA Mega Garchomp Draco Meteor vs. 252 HP / 0 SpD Chesnaught: 273-322 (71.8 - 84.7%) -- guaranteed 2HKO after sandstorm damage and Leftovers recovery
160 Atk Sand Force Mega Garchomp Earthquake vs. 252 HP / 0 Def Clefable in Sand: 238-282 (60.4 - 71.5%) -- guaranteed 2HKO after Leftovers recovery
I think that's enough. In the sand, only physically defensive Deoxys-D can absolutely switch in safely at full health, who so happens to fail to 2HKO our 252 / 0 TTar with 0 Atk Superpower while fearing Dark STAB at -1 or -2 defense.
For this reason, I would personally prefer to run Smooth Rock on TTar so that Megarchomp can stay in for longer. If you opt for Lefties on TTar, Chomp should be quite capable of adopting a hit & run style under the sand, easily denting things each time, given good predictions are made.
Now, TTar might want some explaining, too. For his intentions, he is providing sand for not only his SpD, but for Shuckle's SpD and Chomp's fearsome Quakedge. For his intentions, this TTar's goal is to do a little parashuffling. The choice between Roar and Dragon Tail is whether you want to phase through subs and fairies or phase through taunt and Soundproof. lol, Mr.Mime can't be phazed with either, but it'll never like TWave.
Rock Slide is the stab of choice, synergizing relatively well with TWave while giving it an answer to the likes of Talonflame who want to RK our beloved Chomp and Pinsir lacking CC, but don't expect the latter as much. Then, there's the last slot. With 60 Atk EVs, Pursuit always KOs Latios, who threatens to RK Chomp with Dragon STAB because it bypasses Sticky Web. However, Shuckle could threaten to trap and kill with Infestation, so you may not feel as obligated to run Pursuit. with 100 SpA EVs, Ice Beam brings down Gliscor and Noivern, two moderate concerns for Chomp. Fire Blast is another way to roast steels and is generally a superior standalone coverage move. Thunderbolt becomes a guaranteed KO on Gyarados after even sandstorm damage if you shift the 60 Atk EVs to SpA, but it's really only good for that. Personally, I wouldn't go for it because you'd be better off paralyzing it for Garchomp, and then Rock Slide at it, should it choose to stay in.
Alright, now let's talk about Shuckle. I had to make this guy work. Not only does it provide the webs Chomp craves, but it benefits from the sand Tyranitar lends it.
Just for the lols:
252 SpA Kyogre Surf vs. 252 HP / 4 SpD Shuckle in Rain: 236-278 (96.7 - 113.9%) -- 75% chance to OHKO
252+ Atk Life Orb Adaptability Crawdaunt Crabhammer vs. 252 HP / 252+ Def Shuckle: 229-270 (93.8 - 110.6%) -- 62.5% chance to OHKO
For this Shuckle's job, the first three slots are most important. Generally, the idea is to, yeah, lead with Shuckle. You want to lure a Magic Bouncer/Taunter(yes) and hit it with Infestation on the switch. On a magic bouncer, binding band will most likely be the superior item, since you don't want to toxic yourself, and infestation will be the only residual damage you can inflict. however, from the puny damage you'll take from some of them, leftovers will let you come out of there with more HP at the end. Once the bouncer is discouraged from staying in, you can RK them later for mid-game webs, or take the risk and web as the bouncer switches out. Against pure taunters, Toxic on the switch is much better, as you can Infestation on turn 2 to remove them much more quickly. Knock off is a fine alternative if you refuse to be Taunt bait, removing the item of the Taunter, however pathetic the damage will be.
The fourth slot mostly depends on personal preference. Protect goes well with Leftovers, Rest is appreciated by the Binding Band ones, Stealth Rock is always good to have, and Power Split also likes the Leftovers set.
Now, only run Shell Smash with Contrary leftovers sets. Otherwise, always go with Sturdy, unless you like stray +1 defense boosts from random crunches and shadow balls, but I really wouldn't count on that.