Sylveon should be one of the best Pokemon to use in triple battles as its spread move, Hyper Voice can hit at least 2 Pokemon at the time every time it is used (depending on its position on the field). Due to its great typing, it will often be backed up by a fighting or steel type (i.e Aegislash / Hitmontop) who then again, shield it with Wide Guard.
A very handy moveset would be:
Sylveon @ Leftovers / Expert Belt / Choice Specs
EVs: 244 HP / 252 SAtk / 12 Spe
- Hyper Voice
- Protect / Hidden Power Ground (If specs)
- Shadow Ball / Quick Attack
A little different compared to your Sylveon in OU, but it actually works. Seeing as Hyper Voice will be nuking more than one Pokemon at the time, an Expert Belt can be very handy, while lefties graint your recovery and choice specs is here for the sake of nuking everything. Psyshock is to still be able to hit Pokemon such as Hitmontop when they use a move like Wide Guard to block Hyper Voice from hitting them. SHadow Ball is pretty much your only way of hitting Aegislash for some good damage while Quick Attack, despite odd, can be very nifty in cleaning weakened Pokemon when boosted by Pixilate, however Shadow Ball is usually the better option. Should you be specs, HP Ground is a very nice move to hit Eruption Heatran.
Odd be true, Mega Blastoise is a very dangerous Pokemon in triple battles, as a full health Water Spout will be nuking things when it is supported well by other teammates (Fake out users, etc...) Also wielding the ability to defeat most Wide Guard users due to its excellent offensive typing and nuking ability Mega Launcher, which tends to form an issue for many Pokemon.:
Blastoise @ Blastoisite
Trait: Rain Dish ---> Mega launcher
EVs: 236 HP / 252 SAtk / 20 Spe
- Water Spout
- Aura Sphere
- Dark Pulse
- Water Pulse / Scald / Protect
A pretty straight forward strategy. Spam Water Spout, and once you are weakened till the extent that it won't do jack, spam Water Pulse / Scald. Aura Sphere is just a powerful Mega Launcher boosted move that complements Dark Pulse offensively. With Dark Pulse helping you get passed things such as Aegislash. Protect can also be an option if you really do wish to scout-out your opponents moves.
Hitmontop is a great Pokemon and most likely one of your most reliable Smeargle checks. It is a great Wide Guard user, if not the best in triple battles and is very known for its longevity. While also providing intimdate support and priority.
Hitmontop @ Sitrus Berry
EVs: 252 HP / 136 Atk / 60 Def / 60 SDef
- Fake Out
- Close Combat
- Wide Guard
Hitmontop brings nothing but joy on your face as its great utility enables it to fit on nearly every triple battle team. Also being one of the best checks to Beat-up Terrakion (despite gimmick, can be very deadly if not prepared for). Fake Out is just to stop Pokemon such as Smeargle from spamming Dark Void and granting your team an advantage momentum. CLose Combat is the only STAB you really need as it destroys Terrakion and Heatran. Wide Guard is for obvious reasons, shield teams from powerful spread moves as mentioned above, while Feint is a nifty move to clean up weakened Pokemon with or to still hit Pokemon on a predicted Protect.
Smeargle is a pretty decent Pokemon in triple battles as it basically wields the ability to put all 3 Pokemon on the field to sleep with one move, Dark Void. That's pretty much its only real niche. A very simple moveset, if I must say so myself
Smeargle @ Choice Scarf / Focus Sash
Trait: Own Tempo
EVs: 96 HP / 120 Def / 40 SDef / 252 Spe
- Dark Void
- Fake Out
In all honesty, that's all it needs because it won't be staying around for that long, and for obvious reason. Tbh, the choice scarf set is better than the Focus Sash variant because it can just get ambushed by every single Pokemon on the field and get its Focus Sash broken and it's role destroyed, making it deadweight. It really just spams Dark Void.
Perhaps not the greatest idea, but it will surprise you how many people get caught off-guard by it.
Double Battles (All formats)
Charizard ( X & Y)
Charizard is a great Pokemon in pretty much every tier it is played in. Doubles is no exception.
Both its forms are devastating Pokemon to face once given the slightest oppertunity.
Charizard @ Charizardite Y
Trait: Blaze ---> Drought
EVs: 252 SAtk / 4 Def / 252 Spe (Pure offense) or 252 HP / 12 Def / 92 SAtk / 4 SDef / 148 Spe (survives several rock type moves.)
Timid (Pure offense) / Modest (bulkier variant)
- Heat Wave
- Solar Beam
- Focus Blast
I am pretty sure we all know the devastating power of Mega Charizard Y. The offensive variant just breaks things regardless of their names, while the bulkier variant not only destroys things, but also survives hits a Charizard should NOT be tanking. They are as following:
Survives a Rock Slide from a -1 12 Atk EVs Mega Tyranitar
Survives a Rock Slide from a Jolly Garchomp
Survives a Rock Slide from an LO boosted Timid Salamence
Survives a Return from an Adamant Mega-Kangaskhan
Survives a Thunderbolt from a Modest Mega-Manectric
The moves are pretty self-explanatory.
Charizard @ Charizardite X
Trait: Blaze ---> Tough Claws
EVs: 40 HP / 208 Atk / 32 Def / 228 Spe
- Dragon Dance
- Fire Punch / Flare Blitz
- Dragon Claw
The King of all Dragons. Yeah, this thing is just absurd and rarely struggles to get a DD up. The moves on this set are just for overall superior coverage. After a DD, I am pretty sure you know what it does :I