Zapdos @ Leftovers
Ability: Static
EVs: 252 HP / 6 Def / 252 SpA
Modest Nature
- Discharge
- Heat Wave
- Hidden Power [Ice]
- Roost
This combines utility with power. Zapdos has few weaknesses and with its resistances, it can go toe-to-toe with many different Pokemon. It can switch easily into Steel, Grass, and Bug-type moves and hit their STAB users hard with Heat Wave. It also does well against Fighting- and Flying-types with Discharge; Static and Discharge work together to give you a very good chance of paralyzing other Pokemon (on a turn where Zapdos uses Discharge and an opponent uses a contact move, you have a 51% chance of landing paralysis.)
Many Bug-, Fighting-, Steel-, and Flying-type moves also make contact, so not only does Zapdos switch into them easily, Static punishes their users just from the act of allowing Zapdos to switch in. If they retreat, Discharge can potentially paralyze non-Ground, non-Electric Pokemon they fall back to. Paralyzed targets will almost always be slower than Zapdos, and it even gives it the potential to enable Roost spam--you'd use it contentiously until the opponent becomes fully paralyzed and gives you a free turn.
Both of these are reasons to have Max HP instead of Max Spe, and taking hits better also draws out the usefulness of Lefties and Roost. Hidden Power [Ice] is mainly to strike Ground and Dragon Types, especially Pokemon 4x weak to Ice like Landorus or Garchomp.