I don't want to steal credit, so I'll list a couple of Pokémon I believe have good synergy with Scizor.
Azurill may look puny at first, but it is actually very good in-game. With access to the ability Huge Power, Azumarill essentially has 100 base Attack with Bulk to back it up. When it evolves, Marill has STAB to cover Scizor's Fire Weakness and Scizor covers its Grass and Poison Weakness (by being immune). Azurill is also available on Route 3, leading it to be obtained relatively early. It also covers Grant and Korrina nicely while chipping in with others.
Azumarill @ Anything (Maybe Mystic Water).
Ability: Huge Power
- Aqua Tail/Waterfall (Level 21/HM)
- Play Rough (Level 50). Can use a filler move like Dig until obtained.
- Filler move. Surf/Rock Smash/Strength depending on needs.
Aerodactyl is available in Ambrette Town when you get an Old Amber. To get it you need Rock Smash, but it is well worth it. An Old Amber is found by smashing rocks in Glittering Cave. Once you revive it, Aerodactyl has Bulldoze, preparing you for Grant. In addition, you get Aerodactylite early on, once you find a scientist in Glittering Cave, so this gives you a huge advantage once you get the Key Stone. Having great 135 Attack and 150 Speed is nice. Aerodactyl has coverage for most major battles.
Aerodactyl @ Aerodactylite
Any Ability -> Tough Claws
- Bite -> Crunch (Level 1 and 33)
- Bulldoze -> Earthquake (TM) Bulldoze is available at Lumoise City shop in South Boulevard.
- Rock Tomb/Rock Slide/Stone Edge (TM)
- Aerial Ace/Fly (TM)
As Demon Hunter said, Garchomp and Scizor has nice synergy with Garchomp covering Scizor's weakness and Scizor covering Garchomp's Weakness. Gible is obtained mid-game on Route 13, thus requiring you to Level it up to catch up with your team. Although it evolves later at 48, it is well worth the wait due to its 130 Attack and 102 Speed Stats. Gible already has access to Dragon Claw and Dig, giving it good coverage against the battles of Clemont, as well as most of the Pokémon League.
Garchomp @ Life Orb
252 Atk/ 252 Speed/ 4 Def
Sand Veil Ability. (If you can get Rough Skin, use it though.
- Dragon Claw/Outrage
- Fire Fang
- Swords Dance
Any of these options work fine, but I tend to lean towards Azurill or Aerodactyl because of their much earlier availability. It is your choice of which one to choose since it is most likely in-game, but your choice again.
Edit: Since you said you are looking to battle your friends, I would go with Garchomp. I just edited Garchomp's Moveset to make it more viable to battle your friends.