Forretress @ Leftovers

Trait: Sturdy
EVs: 252 HP / 252 Def / 4 SpD
Nature: Relaxed (+Def, -Spe)
- Stealth Rock
- Spikes/Toxic Spikes
- Rapid Spin
- Gyro Ball/Earthquake
Forretress is a popular lead, setting up Spikes and/or Stealth Rock, also a great Pokemon by spinning away hazards. Sometimes Forretress isn't used first, though.
Deoxys-D @ Leftovers

Trait: Pressure
EVs: 252 HP / 4 SpD / 252 Spe
Nature: Timid (+Atk, -Spe)
- Taunt
- Stealth Rock
- Night Shade
- Recover
I like this one as a lead because most people won't suspect a Taunt coming.
Genesect @ Choice Scarf

Trait: Download
EVs: 4 Atk / 252 SpA / 252 Spe
Nature: Mild (+SpA, -Def)
- U-Turn
- Thunderbolt
- Flamethrower
- Ice Beam
Basic popular Genesect set. With many different type of moves to choose form, it's a great lead.
Politoed @ Leftovers

Trait: Drizzle
EVs: 252 HP / 252 SpD / 4 Def
Nature: Bold (+Def, -Atk)
- Scald/Surf
- Perish Song/Toxic
- Ice Beam
- Encore
Politoed has many different movesets, this is just a general idea.
Since my favorite weather is Rain, I did Politoed. But depending on your weather, you would do different Pokemon.
Sand: Hippowdown / Tyranitar
Sun: Ninetails
Hail: Abomasnow
Breloom @ Toxic Orb

Trait: Poison Heal
EVs: 236 HP / 212 SpD / 60 Spe
Nature: Careful (+SpD, -SpA)
- Spore
- Bulk Up
- Seed Bomb
- Drain Punch
This set is pretty good, countering Politoed's and Sporing other opponents. Then proceed to Bulk Up.
There are many many more.
These are just some leads, if you want more, please comment and I will add some more.