Here are some of the best special sweepers in:
Ubers:
- Kyogre
- Deoxys forms (other than defense)
- Genesect
- Darkrai
- Lucario (Mega)
- Mewtwo (Mega Y as well)
- Shaymin-Sky
- Xerneas
Other mentions include:
- Gengar (Mega)
- Groudon
- Arceus forms
- Reshiram
Darkrai @ Life Orb
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
- Dark Void
- Dark Pulse
- Nasty Plot
- Sludge Bomb
OU:
- Keldeo
- Latios
- Manectric (Mega)
- Venusaur (Mega as well)
- Alakazam (Mega)
- Greninja
- Gardevoir (Mega as well)
- Gengar
- Charizard (Mega Y)
Other good special sweepers include:
- Volcarona
- Thundurus-T
- Tornadus-T
- Manaphy
- Landorus
Greninja @ Life Orb
Ability: Protean
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Hydro Pump
- Ice Beam
- Extrasensory
- Grass Knot
UU:
- Blastoise (Mega)
- Chandelure
- Alakazam
- Espeon
- Hydreigon
- Kingdra
- Nidoking
- Raikou
- Starmie
Other mentions include:
- Goodra
- Galvantula
- Infernape
- Suicune
- Togekiss
- Florges
- Yanmega
- Zoroark
Nidoking @ Choice Scarf
Ability: Sheer Force
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
- Sludge Wave
- Earth Power
- Ice Beam
- Thunderbolt
RU:
- Virizion
- Sharpedo
- Reuniclus
- Jolteon
- Heliolisk
Other mentions include:
- Abomasnow (Mega)
- Clawitzer
- Delphox
- Exploud
Jolteon @ Choice Specs
Ability: Volt Absorb
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Thunderbolt
- Signal Beam
- Hidden Power Water
- Volt Switch
NU:
- Jynx
- Swanna
- Butterfree
- Glaceon
- Ludicolo
- Sceptile
- Xatu
Other mentions include:
- Vivillon
- Samurott
- Mismagius
- Klinklang
- Accelgor
Ludicolo @ Life Orb
Ability: Swift Swim
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Hydro Pump
- Giga Drain
- Ice Beam
- Rain Dance
Hope I helped!