Weezing
Levitate
This Pokémon is immune to Ground moves.
Type Tier
Poison OU
Statistics
Min- Min Max Max+
HP
65
 - 271 334 -
Atk
90
 194 216 279 306
Def
120
 248 276 339 372
SpA
85
 185 206 269 295
SpD
70
 158 176 239 262
Spe
60
 140 156 219 240
Name Item Nature

Defensively Oriented Weezing

 Leftovers Impish / Bold
Moveset EVs
~ Sludge Bomb / Flamethrower
~ Haze
~ Will-O-Wisp
~ Pain Split / Rest
252 HP / 252 Def / 4 Spe

Weezing is the best Fighting Pokémon counter and Hazer in the game. It's a simple set: burn stuff with Will-O-Wisp, Haze if they set-up, and Sludge Bomb or Flamethrower them to death. Steel or Rock-types with Substitute might give you problems here.

Name Item Nature

Offensively Oriented Weezing

 Leftovers Brave
Moveset EVs
~ Sludge Bomb
~ Flamethrower / Fire Blast
~ Haze / Will-O-Wisp
~ Explosion
252 HP / 178 Atk / 68 SpA / 12 Spe

An attacking Weezing. This set actually works really well and can put a dent in stall based teams. The only thing you really need to look out for here is Dusclops / Gengar.

Other Options

Thunderbolt or Thunder works for an alternate attacking option that gives Gyarados trouble. Weezing can use Shadow Ball to hit Dusclops and Gengar a bit harder.

EVs

For a defensive Weezing, you'll want max HP always, because much like Skarmory, Weezing actually gets better physical defense by maxing HP than by putting EVs into Defense. Use a lot of Defense, with a Defense boosting nature. The rest should go in Attack.

A more offensive Weezing can concentrate on Attack and put some EVs in Special Attack to kill Skarmory and Heracross more quickly. The rest in HP is welcome so he can still take a few hits here and there.

Opinion

It resists Megahorn and any Fighting move and has immense Defense, making it an ideal Heracross counter. It can Will-O-Wisp physical attackers and Haze to ruin their set-ups, so he's a great switch-in against Snorlax as well. He gives Baton Pass chains a hard time as long as he isn't put to Sleep or trapped and outstalled, and can live through even the most powerful Focus Punches from the likes of Machamp and Medicham.

Counters

Milotic is a great counter for Weezing, actually taking advantage of the Poison from Sludge Bomb or Burn from Will-O-Wisp. Other counters include Fire Pokémon, especially Houndoom who can Pursuit it on the switch out. Dusclops stops it cold as well. Skarmory can absorb the Will-O-Wisp from the first set, Spike up and Rest off the damage (or get healed by a Blissey or Celebi afterwards). Swellow loves those Burns, and can nearly OHKO Weezing with a Choice Banded Facade, and Ursaring is even worse news.