Actually, I would prefer Zapdos over Raikou, as even though Raikou lacks Rock- and Ice-type weaknesses, Zapdos brings to the table valuable Fighting- and Grass-type resistances, more-or-less the same defenses, higher SpA, LightningRod, and Roost. The set I ran when I used rain was -
Zapdos @ Choice Scarf
move 1: Thunder
move 2: Hidden Power Ice
move 3: Volt Switch
move 4: Toxic / Roost
evs: 252 SpA / 4 SpD / 252 Spe
The premise is simple - use Politoed / Manaphy / other Water-types as a lure to get into Thunderbolt, and go to town with Thunder from 525 SpA. All you need to do is take Ground-types out [this is easy with stuff like Keldeo around], and then you can sweep with just Thunder. Plus Zapdos has enough bulk to take the occasional hit or two from stuff it can't KO with +1 Thunder, like Dragonite. Volt Switch helps to maintain momentum early game, while Hidden Power Ice takes Gliscor out. I experimented a bit with the last slot - while I could occasionally scare a Water-type like Jellicent off and Roost to heal off SR damage, Toxic can directly cripple walls.
Another thing I noticed was running 252 HP / 252 Def Bold Tail Glow Manaphy with Life Orb - this lures in Ferrothorn who think they can take Manaphy out with Power Whip, but Manaphy can get to +6 with greater ease now. A similar set with Calm Mind instead of Tail Glow functions very well as a late-game sweeper, as Manaphy becomes a near-impermeable wall once its checks are weakened or eliminated.