Choice Scarf (Haunter) @ Choice Scarf  
Ability: Levitate  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Shadow Ball  
- Sludge Wave  
- Dazzling Gleam  / Energy Ball / Destiny Bond
- Trick / Destiny Bond

SubWillowisp (Haunter) @ Poisonium Z  
Ability: Levitate  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Substitute  
- Sludge Wave  
- Hex  
- Will-O-Wisp

Life Orb (Haunter) @ Life Orb  
Ability: Levitate  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Sludge Wave  
- Shadow Ball  
- Giga Drain / Hidden Power [Fire] / Hidden Power [Ground] / Hidden Power [Fighting]
- Destiny Bond  

Note: Choice Scarf Hunter is the fastest standard Choice Scarfer in the tier. Great DualSTAB and access to Dazzling Gleam/Energy Ball to kill Krokorok (Energy Ball hits Water Types harder), and Trick to cripple incoming Walls or Destiny Bond if Haunter is low on HP and needs a spesific threat down. Sub + Will O Wisp is to cripple incoming physical attackers that would other wise try to kill it or Pursuit trap, and to Will o Wisp walls for Hex to sting a bit harder, like Gloom and Water types. Life Orb runs the same dual STAB combo as the Scarf set, but Giga Drain as the primary secondary move, as it heals a bit of hp as well as 2hkoing the 2 main bulky water types and OHKOing Marshtomp and Krokorok, doing 10% less than Energy Ball/Thunderbolt which otherwise also just 2HKOs. Hidden Power coverage can be used instead of or along with Giga Drain if needed for spesific pokemons and scenarios.

Checks & Counters: Kadabra can outspeed any variant not being Scarfed, and still live a hit with Focus Sash intact. Pokemons like Metang and Krokorok can also Pursuit Trap if the Scarfer is locked into the wrong move, or if said Krokorok outspeeds. Munchlax and Grimer-Alola can also freely switch in and Pursuit trap. Pokemons like Ferroseed can also cripple with Thunder Wave and Knock Off, and generally anything faster or with a strong Sucker Punch can threaten out Haunter, such as Electabuzz or Pawniard.

Other Options: Taunt can be used to stop pokemons from setting up or crippling Haunter, making it a great stop to the behemoth known as Vigoroth. Toxic is a different option to cripple bulky pokemons that otherwise doesn't ake too much damage, but with Haunters incredible power, there aren't many of those. Knock Off, Sucker Punch and Psychic are all decent options for the Life Orb variant, Psychic and Knock Off especially for other variants as well.