Moves
Will-O-Wisp is one of Weezing's main attributes as a physical wall, allowing it to completely cripple physically offensive Pokemon such as Steelix and Scyther, wearing them down while also making them setup fodder for teammates such as Swords Dance Samurott. Sludge Bomb is a strong STAB Poison-type attack that has a good chance to inflict poison on troublesome Pokemon that may attempt to switch into Will-O-Wisp and other moves, such as Magmortar, Pyroar, and Xatu. Taunt prevents Weezing from being setup fodder for entry hazard setters such as Garbodor and Steelix and sweepers such as Malamar, Mega Audino, and Gurdurr. It also prevents slower defensive Pokemon from healing themselves, such as Vileplume, Quagsire, and Gourgeist-XL. Toxic Spikes allows Weezing to wear down the opponent's team throughout the match if they lack a grounded Poison-type Pokemon, but it will often only be able to set one layer at a time due to how easy it is to force out. Pain Split provides Weezing with semi-reliable recovery and lets it wear down Pokemon such as Lanturn and Hariyama when at low health, being an especially good option if your team lacks Wish support. Clear Smog and Haze can remove boosts from setup sweepers, with the former inflicting damage and bypassing Taunt, while the latter bypasses Substitute and can be used on Steel-type Pokemon. Flamethrower lets Weezing attack Steel-types such as Steelix and Mawile directly, in addition to Substitute Klinklang, but Will-O-Wisp is usually sufficient for dealing with them.
Set Details
Levitate allows Weezing to bypass Ground-type attacks and both Spikes and Toxic Spikes. However, it also prevents Weezing from absorbing Toxic Spikes for its team, so it may need to be paired with a grounded Poison-type or entry hazard controller if desired. Black Sludge provides passive recovery for Weezing while also deterring Trick users such as Choice Scarf Jynx and Rotom from taking advantage of it. 108 Speed EVs allow Weezing to outspeed uninvested Malamar and use Taunt to prevent it from using Rest to heal or remove status, as well as outspeeding Pelipper and Mantine and preventing them from using Defog. The nature and remaining EVs are used to maximize Weezing's HP and Defense so that it can take physical hits throughout the match. If Malamar is not a big threat to the rest of your team, the Speed EVs can be dropped and put in Defense for even more bulk. If Weezing has reliable Wish support, Rocky Helmet can be a good item choice for punishing contact attackers such as Hariyama more effectively, breaking Sturdy, and stacking residual damage.
Usage Tips
Weezing should be used as a pivot to switch into physical attackers throughout the match, either spreading status on the opponent's team with Will-O-Wisp or setting up Toxic Spikes if it gets a chance. Toxic Spikes should not be used until the opponent's grounded Poison-types have been removed. Weezing can switch into bulky setup sweepers such as Malamar, Mega Audino, and Gurdurr and stop them with Taunt, but it usually shouldn't do so against faster Pokemon, as it will likely be hit by a boosted attack before it can do anything. Sludge Bomb can be used to punish usual switch-ins such as Psychic- and Fire-types with a 30% chance to poison, but only if there is little risk in switching to a teammate afterwards. It should also be used with caution when there are specific threats that you don't want to inflict normal poison on, such as Rhydon and Scyther, which Weezing can usually only beat by burning them.
Team Options
Wish support is fantastic to keep Weezing at good health throughout a match, and Mega Audino is good at providing this due to its great bulk and ability to deal with special attackers with either Calm Mind or raw bulk. Specially defensive Pokemon can be used to compensate for Weezing's lack of Special Defense on balanced and defensive teams. Lanturn can deal with Fire-types fairly well and appreciates Weezing's immunity to Ground-type attacks while also providing Heal Bell support for defensive teams. Altaria can similarly remove status and deter setup sweepers with Haze, and it appreciates Weezing dealing with Fairy-types like Mega Audino. Skuntank can trap problematic Psychic-types such as Xatu for Weezing with Pursuit, as well as absorbing Toxic Spikes for defensive teams and appreciating Weezing's Levitate. Dark-type Pokemon in general, such as Malamar and Shiftry, are also good responses to Psychic-types. Stealth Rock users such as Steelix and Rhydon can punish Fire-type Pokemon for switching into Weezing and help it stack residual damage on the opponent's team. Cacturne is a good Spikes user for balanced teams that also threatens Psychic-types. Weezing synergizes particularly well with these candidates due to Levitate and its Fighting-type resistance. Finally, if Weezing runs Toxic Spikes, Ghost-type Pokemon such as Rotom and Mismagius can capitalize on them, as they can use Hex against targets immediately instead of having to spend a turn burning them, and they can also prevent foes from using Rapid Spin to remove these entry hazards.