Might as well add one of my personal favorites. This set is really good and I think more people should use it.
[SET]
Latias (F) @ Soul Dew
Trait: Levitate
EVs: 200 HP / 56 SAtk / 252 Spd
Timid Nature
- Calm Mind
- Recover
- Dragon Pulse
- Refresh
Role: Special Sweeper, Stallbreaker
What it does: Latias is an awesome Calm Minder, but status puts it to a halt. Not with Refresh! With Refresh, Latias sets up against everything it once had to flee in fear from, such as Chansey, Toxic Forretress and Tentacruel, and CM Arceus formes sans Ghost, Dark, and Bug. Mono-Dragon coverage is excellent in a metagame where there are few Steel-types that can even harm it. Literally the only Steel-type in the game not 2HKOed by Dragon Pulse at +6 is 252/252+ Arceus-Steel, and even that is only if Stealth Rock is absent. With power like that, only minimum Special Attack investment is needed. 56 EVs guarantee the OHKO against 0/0 Palkia at +0 after SR damage, and allows for the 2HKO against that Arceus set after SR, but if you don't need that you can always run full HP investment. This added bulk makes it far easier to set up multiple CM boosts, and without Toxic to put a timer on Latias, most stall teams are crushed beneath Latias's blows. Its excellent Speed means that no enemy Dragon-types can take advantage of Latias's weaker defenses at +0 unless they are using a Choice Scarf. If you feel like stall is giving your team problems, give Latias a try and watch stall teams melt away!
Good Teammates: Latias needs powerful physical threats, such as Extreme Killer Arceus and Zekrom, removed before it can pull off a sweep. Terrakion can beat Arceus to death while also softening up Steel-types. As for Zekrom, a Steel-type of your own, such as Ferrothorn, can eat Zekrom's Outrages all day and cripple it with Thunder Wave or slowly sap its health with Leech Seed and Iron Barbs. It can also set hazards to help Latias gain more KOs.
What counters it: Anything faster with a physical attack, such as SD Arceus formes, Scarf Zekrom, and Genesect, can outspeed and deal harsh damage to Latias. Arceus can set up on Latias if it hasn't boosted yet, and then knock it out with an ExtremeSpeed. Zekrom can use Outrage to squash Latias easily. Genesect gets an Attack boost from Download and has U-turn to abuse it with, but since its Attack stat is usually uninvested, it requires some prior damage to score a KO.