Just my try at a rain team.
Politoed @ Leftovers
Modest
252 HP/252 SpA/4 Spe
Drizzle
Hydro Pump
Focus Blast
Psychic
Hidden Power [Electric]
Politoed is the only Pokemon outside of Ubers to have Drizzle, so it's a must have for a Rain Team. Although, that's not it's only use. It has a fairly high SpA stat, so that can be used by giving it a few good Special attacks with fairly high base power.
Zapdos @ Life Orb
Modest
4 HP/252 SpA/252 Spe
Lightningrod
Thunder
Roost
Hidden Power [Water]
Ancientpower
Zapdos with Lightningrod makes it more useful on a rain team. It still has high SpA and Thunder, but now it can switch in and take all water weaknesses, because it resists grass and Lightingrod gets the electric. Roos is to keep it around longer, Hidden Power is for pesky Rock/Ground types.
Empoleon @ Leftovers
Modest
4 HP/252 SpA/252 SpD
Defiant
Hydro Pump
Grass Knot
Ice Beam
Hidden Power [Fire]
Empoleon is a nice Pokemon, and it covers the Rock/Dragon weaknesses that Kyurem has. Nice SpA stat like the previous two Pokemon, and has access to some nice moves.
Bouffalant @ Life Orb
Adamant
252 HP/252 Att/4 Spe
Sap Sipper
Megahorn
Iron Head
Poison Jab
Wild Charge
Bouffalant is the major Grass resistance on the team, with Sap Sipper making him more powerful, and an already high attack stat, he can dominate. Some nice moves, for good coverage.
Kyrurem @ Focus Sash
Naive
252 Att/252 SpA/4 Spe
Pressure
Stone Edge
Dragon Claw
Ice Beam
Shadow Ball
Kyurem is the mixed attacker of the team. 130 base Attack and SpA, it can hit hard, ans with some good STAB attacks, you'll be destroyed.
Rotom-W @ Chesto Berry
Modest
128 Def/252 SpA/128 SpD
Levitate
Hydro Pump
Dark Pulse
Thunder
Rest
The Wall/Attacker. 107 base Def and SpD, it's be foolish not to take advantage of them. Some nice moves, too. Rest + Chesto so it can stay around longer.
Politoed @ Leftovers
Modest
252 HP/252 SpA/4 Spe
Drizzle
Hydro Pump
Focus Blast
Psychic
Hidden Power [Electric]
Politoed is the only Pokemon outside of Ubers to have Drizzle, so it's a must have for a Rain Team. Although, that's not it's only use. It has a fairly high SpA stat, so that can be used by giving it a few good Special attacks with fairly high base power.
Zapdos @ Life Orb
Modest
4 HP/252 SpA/252 Spe
Lightningrod
Thunder
Roost
Hidden Power [Water]
Ancientpower
Zapdos with Lightningrod makes it more useful on a rain team. It still has high SpA and Thunder, but now it can switch in and take all water weaknesses, because it resists grass and Lightingrod gets the electric. Roos is to keep it around longer, Hidden Power is for pesky Rock/Ground types.
Empoleon @ Leftovers
Modest
4 HP/252 SpA/252 SpD
Defiant
Hydro Pump
Grass Knot
Ice Beam
Hidden Power [Fire]
Empoleon is a nice Pokemon, and it covers the Rock/Dragon weaknesses that Kyurem has. Nice SpA stat like the previous two Pokemon, and has access to some nice moves.
Bouffalant @ Life Orb
Adamant
252 HP/252 Att/4 Spe
Sap Sipper
Megahorn
Iron Head
Poison Jab
Wild Charge
Bouffalant is the major Grass resistance on the team, with Sap Sipper making him more powerful, and an already high attack stat, he can dominate. Some nice moves, for good coverage.
Kyrurem @ Focus Sash
Naive
252 Att/252 SpA/4 Spe
Pressure
Stone Edge
Dragon Claw
Ice Beam
Shadow Ball
Kyurem is the mixed attacker of the team. 130 base Attack and SpA, it can hit hard, ans with some good STAB attacks, you'll be destroyed.
Rotom-W @ Chesto Berry
Modest
128 Def/252 SpA/128 SpD
Levitate
Hydro Pump
Dark Pulse
Thunder
Rest
The Wall/Attacker. 107 base Def and SpD, it's be foolish not to take advantage of them. Some nice moves, too. Rest + Chesto so it can stay around longer.