[WildAce]

ZAPDOS:

Zapdos @ Leftovers
Ability: Pressure
Nature: Modest
Evs: 252 Sp.ATK / 220 HP / 36 Speed
- Charge Beam / Substitute
- Thunderbolt / Discharge / Thunder Wave
- Roost
- Baton Pass / HP: Grass / HP: Ice

Aah Zapdos. My first Legendary love from RBY.
The EVs given here allow it to outspeed Jolly TTar by 2 points (useful for outspeeding things that usually try to outspeed Jolly TTar by only 1 point).
Anymore than that is not necessary due to Discharge / Thunder Wave.
While on that, use Charge Beam with Discharge, and Thunderbolt with ThunderWave.

The first set combination is pretty simple:
Power up your Sp.ATK with Charge Beam, Paralyze / deal damage with Discharge, and recover off damage with Roost.
The Hidden Power depends on your team's needs.

As an alternative, Substitute works wonders if you're not to keen on relying on Charge Beam's overall 63% chance to boost your Sp.ATK. Furthermore, it compliments Zapdos's "good" defenses as well as Roost.

If you can not obtain Hidden Power, then Baton Pass works for a totally different strategy:
Basically, you pass the Sp.ATK boosts to something else (duh...).

Zapdos @ Leftovers
Ability: Pressure
Nature: Modest
Evs: 252 Sp.ATK / 252 Speed / 4 HP
- Substitute
- Thunderbolt / Charge Beam
- Roost
- HP: Grass / HP: Ice / Baton Pass

This set is a "cut and dry" Sweeper variant.
Things should be pretty self-explanatory here. IF (and really IF) you feel that you don't need Thunderbolt, you can drop it for Charge Beam...however ONLY do that for the BP version.

Pure Baton Passer:

Zapdos @ Leftovers
Ability: Pressure
Nature: Modest
Evs: 252 HP / 132 DEF / 40 Speed / 84 Sp.ATK
- Charge Beam / Thunderbolt
- Agility
- Baton Pass
- HP: Grass / HP: Ice / Substitute

Nature / EVs Courtesy of Mekkah from Smogon.com.

Basically, use Agility + Baton Pass...simple eh?

Charge Beam can also provide you with Sp.ATK Boosts to Pass.
Hidden Power is almost a necessity since you will be walled...however, if you're unable to obtain it, Substitute is an EXCELLENT replacement (adding more support for Baton Passing).

Metal Sound Zapdos:

Zapdos @ Leftovers
Ability: Pressure
Nature: Modest / Timid
Evs: 252 Sp.ATK / 252 Speed HP / 4 HP
- Thunderbolt
- Metal Sound
- Roost / Roar / Substitute
- HP: Grass / HP: Ice

Credit for the development of this set goes to Smogon.com
Credit for reminding me to put this set up goes to ELLY.

Basically, Metal Sound will force switches like crazy (even Blissey will consider switching).
If you expect that switch, either Sub or attack accordingly.