Weezing's stats:
65 HP
90 attack
120 defense
85 special attack
70 special defense
60 speed
Ability-Levitate
Notable Moves:
Haze
Sludge Bomb
Explosion
Destiny Bond
Memento
Toxic
Thunderbolt/Thunder
Flamethrower/Fire Blast
Shadow Ball
Will-o-wisp
Gyro Ball
Substitute
Taunt
Protect
Return/Frustration
Pain Split
Dark Pulse
Sleep Talk
Rest
Curse
Clear Smog
One example set:
Curzing
James the Weezing @ Leftovers/Chesto Berry
Ability- Levitate
Careful Nature. 252 HP, 252 sp. def, 4 def
Curse
Rest/Pain Split
Gyro Ball
Sleep Talk/Explosion/Return
Don't know how this would work, but I'm just providing basic data on Weezing. The Curse set allows Weezing to attack on the physical side. Curse boosts its attack and defense while lowering its speed. Rest increases it durability, and Weezing can use Chesto Berry to wake up or resort to Sleep Talk. The speed drop from Curse can boost the power of Gyro Ball to high levels. Finally, explosion and Return are more like coverage moves, with Explosion seeming like a middle finger to the opponent, and Return for some more coverage, also dealing with Gyro Ball's low 8 PP. Pain Split can be used over Rest for Pseudo-recovery
Physical Tank
James the Weezing @ Leftovers
Ability- Levitate
Bold Nature. 252 HP, 252 def, 4 sp. def
Flamethrower/Haze/Clear Smog
Thunderbolt/Haze/Clear Smog
Pain Split
Will-o-wisp/Toxic
What this set does is act like a physical tank and haze set-up sweepers. Flamethrower and Thunderbolt are his coverage moves, while Haze or Clear Smog can be used over either two moves to remove status buffs. Pain Split is his pseudo-recovery, and Will-o-wisp can spread status, further boosting his physical defense. Toxic can be used to force Blissey and Chansey out.
Teammates:
Good teammates for both sets are Dugtrio, Wobbuffet, and Magnezone, who can all trap steel types and KO them, seeing as all of them wall Weezing pretty nicely. A special wall would also be great, such as Tyrannitar, who can take psychic moves and has a boosted special defense in sand, and Blissey/Chansey, both which have amazing special defense stats. Weezing also resists the fighting types attacks all three of them hate, and is immune to ground, which Tyrannitar also dislikes. Heatran can also function as a special wall of the ball of gas, taking special hits that Weezing can't take.
Threats:
If Weezing doesn't have Thunderbolt, Heatran can wall him for all eternity. Steel types in general wall the Curse set, but they must be wary of a Flamethrower or Thunderbolt from the Physical Tank. Powerful Special attackers, such as Alakazam, Mismagius, and Espeon, can all nail him on his only one weakness: Psychic. Taunt would also be a pain to Weezing, as then set-up sweepers can set up, though a Clear Smog will wipe the grins off all their faces if they're not a Jirachi. SubCM Latias and Jirachi can set up on Weezing that don't have Haze, though the former has to beware of Gyro Ball. Finally, this guy is pretty slow, so it is rather easy to Encore him on a useless move and use him as set-up bait.
That's all I have for now, hope it helps. Remember, you don't have to make a pokemon the star of the team. It can also function greatly as a support pokemon or a wallbreaker.