Probably too broad for a thread but I'll answer your question anyway.
Mega Tyranitar is a little overrated in my opinion. It's a good but not great Pokemon, something that can struggle with stall but has numerous offensive checks and a vulnerability to priority. Mega Tyranitar can set up on pretty much anything at full health and can easily lead comebacks late game, but while Tyranitar can take any non-Mach Punch priority, it can't do that AND set up on something like, say, LO Greninja. So it needs proper support, like anything else. (But MegaTar especially.)
Standard DD MegaTar:
Tyranitar @ Tyranitarite
Trait: Sand Stream
EVs: 252 Atk / 4 Def / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Dragon Dance
- Stone Edge / Crunch
- Earthquake
- Ice Punch
Dark is an amazing attacking type and can be used over Stone Edge (with Crunch), but Stone Edge's extra power is often helpful and you can avoid Rocky Helmet damage.
Anyway, MegaTar can support itself somewhat by Earthquaking Conk switch-ins or Stone Edging Azu switch-ins, but for the most part it's going to want some support from team members. You'll want a Stealth Rock setter, so keep that in mind. Every offensive Pokemon (and team) needs it to help weaken opposition and tax switching.
I like Rotom-W as a good partner. It can come in on many offensive checks to Tyranitar, like Keldeo, Sand Rush Excadrill, and Scizor and spread burns and pivot with Volt Switch. It also gives you a better Talonflame check than Tyranitar so you don't wear down Tar's bulk from taking U-turns or even Brave Birds from Talonflame, and in general it's a nice defensive backbone to have on the right team. It's pretty easy to wear down though, so don't be too reckless while using it.
Rotom-W @ Leftovers / Chesto Berry
Trait: Levitate
EVs: 252 HP / 252 Def / 4 SAtk
Bold Nature (+Def, -Atk)
IVs: 0 Atk
- Will-O-Wisp
- Volt Switch
- Hydro Pump
- Pain Split / Rest
I suspect that there's a better EV spread somewhere.
More importantly, you'll want something with good offensive synergy to pair with MegaTar. One option is the incredibly powerful Landorus:
Landorus @ Life Orb
Trait: Sheer Force
EVs: 4 Atk / 252 Spd / 252 SAtk
Naive Nature (+Spd, -SDef)
- Earth Power
- Focus Blast
- Psychic
- Knock Off / Stealth Rock
Landorus is a good breaker to pair with your sweeper, and it basically 6-0es any stall without Gliscor. It can double switch into a weakened Conkeldurr and KO it with Psychic. It can even sac itself in a 1v1 situation against Azumarill and severely weaken it with Earth Power. But really, it just punches holes in most everything and will make Tyranitar's job easier, and Tar can support it with some SS chip damage. Stealth Rock is an option over Knock Off if you can't find room for a setter, in which case you should run Timid. The downside to Landorus is that it invites Keldeo to spam Scald on revenge kills, but you also have four team slots to patch this problem up. However, it also draws in Lati@s, a Pokemon that might be worth sacking Landorus to late-game to set up with Tyranitar.
I won't provide the set, but Excadrill (either Sand Rush or Mold Breaker) can provide SR or hazard control and can threaten offense with Rush or balance with Mold Breaker, but I wouldn't use it with Landorus unless you want incredibly questionable defensive synergy.
Another solid choice is Choice Band Azumarill:
Azumarill @ Choice Band
Trait: Huge Power
EVs: HP / 252 Atk / Spd
Adamant Nature (+Atk, -SAtk)
- Play Rough
- Aqua Jet
- Superpower
- Knock Off / Waterfall
This does a few things for your team. First, it helps with Conkeldurr somewhat and can take back momentum from teams that run it, potentially by double switching into it from Tyranitar. Second, it gives you much-needed priority and a way to check opposing Sand Rush Excadrill, important since you are running Sand yourself. Third, Superpower and Knock Off are great wall-breaking tools to further soften up opponents. In particular, Superpower destroys Ferrothorn, a hard counter to Tyranitar, while Knock Off generally softens up a bunch of Pokemon. By wary of MegaSaur. The problem with Azumarill is that it has some overlapping weaknesses, but it's pretty much always a good choice on offense teams for its defensive typing, offensive power, and priority.
Amoonguss is a god, if you're looking for a more bulky team. Aegislash is pretty much always a good choice.
But yeah, just some suggestions. You'll have to round it out, especially defensively, and I certainly wouldn't use everything I said together. That's really all I'm going to say though since it's your team to build. Good luck.
