Moves
Destiny Bond is for when Haunter is greatly weakened, as it allows Haunter to potentially take a threat down with it. However, Haunter does not appreciate being locked into it, especially since foes can use it as setup fodder. Trick is used to cripple bulky Pokemon that may try to switch in on Haunter, like Audino and Type: Null, and gives Haunter potentially useful items such as Leftovers and Eviolite. Will-O-Wisp is an alternative that can cripple offensive Pokemon that may try to switch in against Haunter such as Kangaskhan and Scyther. It even allows Haunter to take a Pursuit from a non-Black Glasses Jolly Skuntank, and potentially Spiritomb, if switching out at full health.
Set Details
Choice Scarf allows Haunter to outspeed foes such as Choice Scarf Kabutops while Speed tying with Pokemon like +1 Jynx and Choice Scarf Primeape. Levitate makes Haunter immune to all Ground-type attacks, Spikes, and Sticky Webs.
Usage Tips
Haunter is best used as a revenge killer or late-game cleaner. However, Haunter can also utilize its good offensive typing to serve as an offensive check to various Pokemon such as Golurk, Alolan Raichu, and Tangela throughout the game. Haunter should be brought in after a teammate has been KOed or through a slow pivot such as Lanturn or Eelektross; due to its low bulk, Haunter should rarely be switched directly into an attack, even resisted ones. If switching into an immunity, it should still watch out for coverage such as Gurdurr's Knock Off. Haunter similarly can be switched into a predicted harmless status move such as Clefairy's Stealth Rock or Soft-Boiled, but it still has to watch out for moves like Thunder Wave. When Haunter is brought in, stay aware of what checks the opponent has for it, as it will be locked into the same move until it is switched out. This is especially important if their switch-ins include Pursuit users such as Skuntank and Spiritomb, which can Pursuit trap Haunter with ease if they manage to come in when it is locked into a resisted move. If Dark-types pose a threat to the rest of your team, Haunter can use Destiny Bond in such situations. Destiny Bond can also be used to take out any other potential threats to the team or pick off a foe late-game if Haunter is weakened or has no more use. On the other hand, be careful when using Destiny Bond, as it can be exploited by the opponent and be a huge momentum drain. Watch out for any potential Choice Scarf users with naturally higher Speed such as Dodrio and Swanna, as they could otherwise lure Haunter in, thinking it can outspeed. If facing bulkier teams, in which case Haunter's Choice Scarf is not needed, Haunter can use Trick to switch between moves and potentially cripple a foe in the process.
Team Options
Haunter works well on offensive and balance teams in need of a way to keep faster foes in check. Wallbreakers such as Aurorus and Kangaskhan can help weaken the opposing team before Haunter comes in to clean. They can also help against some walls that give Haunter trouble, such as Articuno and Audino, while in return Haunter can cripple Pokemon that wall them such as Type: Null and Regirock with Trick. Haunter also struggles against Dark-types, so checks to them such as Silvally-Fairy, Gurdurr, and Hitmonchan are vital. The latter two also appreciate Haunter's ability to offensively check Psychic-, Fairy- and Ghost-types such as Musharna, Alolan Raichu, and Oricorio-G. Similarly, Water-, Rock-, and Ground-types such as Carracosta, Lycanroc, and Mudsdale benefit from Haunter’s ability to check Grass-types such as Lurantis and Tangela. All three can serve as wallbreakers or provide Stealth Rock to weaken foes, depending on their set. The former two also value Haunter's immunity to Fighting and Ground, although due to Haunter's poor bulk, more reliable checks such as Claydol are recommended. Slow pivots such as Eelektross, Lanturn and Type: Null can get Haunter onto the field safely. Eelektross also has access to Knock Off, which can cripple Eviolite and Assault Vest users such as Type: Null and Hitmonchan. Finally, Haunter can be run alongside other Pokemon that often use Choice Scarf such as Swanna, as this can create mind games for the opponent.