Actually, I choose a different moveset for Mew, since Mewtwo can do that moveset better.
Mew @ Leftovers / Choice Band
Trait:Synchronize
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Earthquake / Explosion
- Hypnosis / Substitute
- Shadow Ball
- Swords Dance / Focus Punch
No one expects a physical Mew, and since most ubers are special-based, this thing can suprise and terrorize. Swords Dance increases Atk by 2x, making up for the lack of a physical STAB. You can go the Hypnosis route or the SubPunch route, or even a combo for a Choice Band route.