Alright, I'll ship for one of my favorites (and probably my most used Pokemon in Battle Spot Singles) as well:
Aerodactyl (Mega) -> B
Here's a sample set for it (because, honestly, I despise the Jolly non-HA sets that apparently are the most common on the cartidge):
Aerodactyl @ Aerodactylite
Ability: Unnerve -> Tough Claws
EVs: 252 Atk | 4 Def | 252 Spe
Nature: Adamant
Taunt | Stone Edge | Earthquake | Ice Fang
What does Aerodactyl do?
A little bit of everything. It's a decent Pokemon to lead with, even though it doesn't really do much against Mamoswine and other rising trends (i.e. Thundurus, which can paralyze you before dying to a Stone Edge), just because it can catch the likes of Garchomp off guard thanks to Ice Fang and deny Hippowdon (and other Pokemon) from getting Stealth Rock up. Besides that, it can also serve as an above-average late game cleaner thanks to the combination of its speed, coverage and power, as well as a Talonflame check (note: it needs 68 Defense EVs in order to tank a Choice Band Talonflame without getting 2HKOd, but it can handle every other variant without investment just fine). It destroys Mega Salamence without giving up momentum too!
It's also worth mentioning that Aerodactyl can actually tank some moves surprisingly well:
- 0 SpA Rotom-W Hydro Pump vs. 0 HP / 0 SpD Mega Aerodactyl: 134-162 (86.4 - 104.5%) -- 25% chance to OHKO
- 252 Atk Adaptability Mega Lucario Bullet Punch vs. 0 HP / 0 Def Mega Aerodactyl: 116-140 (74.8 - 90.3%) -- guaranteed 2HKO
- 252 Atk Garchomp Outrage vs. 0 HP / 0 Def Mega Aerodactyl: 118-139 (76.1 - 89.6%) -- guaranteed 2HKO
- 252+ Atk Parental Bond Mega Kangaskhan Double-Edge vs. 0 HP / 0 Def Mega Aerodactyl: 94-111 (60.6 - 71.6%) -- guaranteed 2HKO
- 252 SpA Mega Gengar Shadow Ball vs. 0 HP / 0 SpD Mega Aerodactyl: 87-103 (56.1 - 66.4%) -- guaranteed 2HKO
Why would you use Mega Aerodactyl despite the opportunity cost?
If what I wrote above isn't enough to convince people, then all I can say is that Aerodactyl is a baller. Seriously, it has such a cool design that it's worth using for that alone :) Seriously though, I believe that Aerodactyl goes really well with this metagame just because a well played Aerodactyl gives so much momentum to its user it's not even funny, and early momentum is even more important here than in Smogon formats. Opportunity cost isn't as big in Battle Spot Singles anyways due to the fact that you can carry 2 Mega Evolutions in a single team without losing much.
Why is this set superior to Jolly non-HA Aerodactyl?
I kind of lied because the ability doesn't really matter (HA is just aesthetically cooler and can actually come in handy more often than Pressure/Rock Head), but Jolly Aerodactyl is just too weak. For the record, Jolly Mega Aerodactyl's Earthquake only OHKOs Mega Lucario 43% of the time while Adamant does it 99% of the time, which is
big. Adamant Mega Evolved Aerodactyl only misses out on Mega Beedrill, Mega Sceptile and Adamant Choice Scarf Landorus-Therian. The first two aren't really relevant and Jolly Aerodactyl can't OHKO Landorus-Therian anyways.
Note: Stealth Rock is actually decent over Taunt if your team's lacking on a Stealth Rock setter, but after trying both I feel that Taunt is vastly superior.
RE: Tornadus-T
I actually have a good soft reset'd Tornadus ready to try and have looked for possible sets for it. Icy Wind looks really neat just because it allows you to get past Rock Tomb Garchomp. I'll probably write about this once I get around to test it though, just because I think it has a lot of potential (even more than C/C+ potential)