Klefki @ Light Clay
Bold nature
Prankster
252 HP/128 def/128 sp.def
-Foul Play
-Swagger
-Light Screen
-Reflect
Dual screener (with swagger + foul play as a backup option). Mostly support, but can also deal decent damage. Setting up dual screens allows Salamence to set up Dragon Dance without worrying about being KO'd, allows Heatran to set up Will-O-Wisp more safely, or provides safer opportunities for the sweepers with poor defenses to switch in. I use him over an Alolan Ninetales because A-Nintales has poor defensive typing, no access to Prankster, and the hail is more of a hindrance to the rest of the team than a benefit.
Salamence @ Salamencite
Jolly nature
Intimidate
4 HP/252 atk/252 spe
-Dragon Dance
-Dragon Claw
-Earthquake
-Double-Edge
Primary physical sweeper, with Dragon Dance as a set-up move. I'm considering replacing Dragon Claw with a better coverage move (particularly an unexpected one like Fire Fang, which would allow her to better counter Celesteela - one of the most major threats to this set). Double-Edge provides a good stab, and Earthquake is good for coverage.
Heatran @ Shuca Berry
Modest nature
Flash Fire
252 HP/4 def/252 sp. atk
-Flash Cannon
-Flamethrower
-Will-O-Wisp
-Earth Power
Special tank, also meant to counter what Salamence can't take down. Shuca berry is to deal with the 4x ground weakness, though a life orb might be a better choice - I chose the berry because she already has decent attacking power. Will-O-Wisp makes up for her poor defense to some extent. The rest is for taking down as many opposing mons as possible.
Tapu Koko @ Electrium Z
Naive nature
Electric Surge
4 HP/252 sp. atk/252 spe
-Thunderbolt
-Volt Switch
-Dazzling Gleam
-Grass Knot
Special sweeper + Z-move user for the team. Might change it to mixed sweeper (with Brave Bird + a physical stab move). Volt Switch is there to get out while still doing some damage. Grass Knot is unexpected (I think?) and deals with most ground-types. Dazzling Gleam and Thunderbolt are for good stab. Still considering replacing it with a different mon (Xurkitree, Mega-Manectric, or possibly a different one if anyone has any suggestions). Hidden Power would have been used, but it has Dark-type HP which isn't very good.
Bisharp @ Choice Scarf
Adamant nature
Defiant
4 HP/252 atk/252 spe
-Iron Head
-Night Slash
-Stone Edge/Rock Tomb?
-Brick Break
Physical sweeper #2. Still considering replacing her with a Breloom or something, especially since having three steel-types is a bad idea and leaves the team vulnerable to ground-types. Brick Break is to deal with opposing dual screens. Night Slash is used here because it is less situational than Sucker Punch, and the Choice Scarf helps to remedy her poor speed. Rock Tomb would be for speed control if used, while Stone Edge does more damage and still provides coverage.
Espeon @ Choice Specs
Timid nature
Magic Bounce
4 HP/252 sp. atk/252 spe
-Psychic
-Psyshock
-Dazzling Gleam
-Shadow Ball
Special sweeper #2. Magic Bounce lets her switch in on status moves that would harm the rest of the team (providing a good counter to Toxic stallers and Will-O-Wisp users). Choice Specs boosts the power of her attacks, but a scarf may be used instead if Bisharp is cut from the team/uses a different item (due to the Battle Spot's item clause). Psyshock also lets her deal with specially defensive Pokemon.
Overall notes:
The team's main purpose is to set up dual screens and then switch in a sweeper without risk of being OHKO'd, allowing them to either set up or just sweep the opposing team. It is built around the core of Salamence and Heatran, who check each other's type weaknesses fairly well while also doing great damage to the opposing Pokemon. However, Tapu Koko, Bisharp, and Espeon might be replaced with different mons that would suit the team better. Also, I've heard it might be best to have two megas in BS singles, since having 3 Pokemon per match might leave me without a mega at times. I'm also not sure that my item and move choices are the best.
Bold nature
Prankster
252 HP/128 def/128 sp.def
-Foul Play
-Swagger
-Light Screen
-Reflect
Dual screener (with swagger + foul play as a backup option). Mostly support, but can also deal decent damage. Setting up dual screens allows Salamence to set up Dragon Dance without worrying about being KO'd, allows Heatran to set up Will-O-Wisp more safely, or provides safer opportunities for the sweepers with poor defenses to switch in. I use him over an Alolan Ninetales because A-Nintales has poor defensive typing, no access to Prankster, and the hail is more of a hindrance to the rest of the team than a benefit.
Salamence @ Salamencite
Jolly nature
Intimidate
4 HP/252 atk/252 spe
-Dragon Dance
-Dragon Claw
-Earthquake
-Double-Edge
Primary physical sweeper, with Dragon Dance as a set-up move. I'm considering replacing Dragon Claw with a better coverage move (particularly an unexpected one like Fire Fang, which would allow her to better counter Celesteela - one of the most major threats to this set). Double-Edge provides a good stab, and Earthquake is good for coverage.
Heatran @ Shuca Berry
Modest nature
Flash Fire
252 HP/4 def/252 sp. atk
-Flash Cannon
-Flamethrower
-Will-O-Wisp
-Earth Power
Special tank, also meant to counter what Salamence can't take down. Shuca berry is to deal with the 4x ground weakness, though a life orb might be a better choice - I chose the berry because she already has decent attacking power. Will-O-Wisp makes up for her poor defense to some extent. The rest is for taking down as many opposing mons as possible.
Tapu Koko @ Electrium Z
Naive nature
Electric Surge
4 HP/252 sp. atk/252 spe
-Thunderbolt
-Volt Switch
-Dazzling Gleam
-Grass Knot
Special sweeper + Z-move user for the team. Might change it to mixed sweeper (with Brave Bird + a physical stab move). Volt Switch is there to get out while still doing some damage. Grass Knot is unexpected (I think?) and deals with most ground-types. Dazzling Gleam and Thunderbolt are for good stab. Still considering replacing it with a different mon (Xurkitree, Mega-Manectric, or possibly a different one if anyone has any suggestions). Hidden Power would have been used, but it has Dark-type HP which isn't very good.
Bisharp @ Choice Scarf
Adamant nature
Defiant
4 HP/252 atk/252 spe
-Iron Head
-Night Slash
-Stone Edge/Rock Tomb?
-Brick Break
Physical sweeper #2. Still considering replacing her with a Breloom or something, especially since having three steel-types is a bad idea and leaves the team vulnerable to ground-types. Brick Break is to deal with opposing dual screens. Night Slash is used here because it is less situational than Sucker Punch, and the Choice Scarf helps to remedy her poor speed. Rock Tomb would be for speed control if used, while Stone Edge does more damage and still provides coverage.
Espeon @ Choice Specs
Timid nature
Magic Bounce
4 HP/252 sp. atk/252 spe
-Psychic
-Psyshock
-Dazzling Gleam
-Shadow Ball
Special sweeper #2. Magic Bounce lets her switch in on status moves that would harm the rest of the team (providing a good counter to Toxic stallers and Will-O-Wisp users). Choice Specs boosts the power of her attacks, but a scarf may be used instead if Bisharp is cut from the team/uses a different item (due to the Battle Spot's item clause). Psyshock also lets her deal with specially defensive Pokemon.
Overall notes:
The team's main purpose is to set up dual screens and then switch in a sweeper without risk of being OHKO'd, allowing them to either set up or just sweep the opposing team. It is built around the core of Salamence and Heatran, who check each other's type weaknesses fairly well while also doing great damage to the opposing Pokemon. However, Tapu Koko, Bisharp, and Espeon might be replaced with different mons that would suit the team better. Also, I've heard it might be best to have two megas in BS singles, since having 3 Pokemon per match might leave me without a mega at times. I'm also not sure that my item and move choices are the best.