Mew is often used as a support in the most teams and this set is used to surprise your opponent by blasting away one or two of there pokemons as they assume it's a support.
Mew's offensive movepool is amazing. Where most pokemons have to use hidden power to cover something Mew don't have that problem as it can learn any tm and move tutor (except draco metreor) from gen 3 and forward.
So here's set on stage Gimmick Killer Mew
Mew @ Life Orb
EVs: 4 Atk / 252 SAtk / 252 Spd
- Fire Blast
- Ice Beam
- Giga Drain/Energy Ball/Thunderbolt/Thunder
This movepool is used for maximum coverage.
Fire blast (in rain) always ohko 248/8 Scizor without stealth rock and deals 79-94% of 252/252+ Forretress health.
Ice beam is ice beam and it hits all dragons hard (bar Kindra)
Superpower takes care of things like Heatran and Tyranitar realy hard, unless they invests in defence and hp.
the last slot is up to you. giga drain heals you and hits water types for plenty of damage. energy ball hits slightly harder but don't heal you.
thunderbolt can be used for more for more power and hits everything bar gastrodon hard. thunder should be used on a rain team.
Gimmick killer Mew loves slower and/or paralyzed foes as they can just be taken care of. Mew also like support in form of wish so it can keep on killing stuff. Jirachi is great partner as it can abuse wish and T-wave or body slam.
Priority moves and faster hardhitting foes will be your doom. The best way of taking care of Mew is by revenge killing it but that can be hard without persuit as you can just switch out. Hazards and status problems is something Mew hates as it limits it life spawn every time it switches in.
A missprediction from your side and you will find yourself in tought spot so good prediction is needed.
Give it some love and it can shine with the right support.