http://www.smogon.com/bw/pokemon/jirachi/ou
[SET]
name: All-Out Physical Attacker
move 1: Meteor Mash
move 2: Ice Punch
move 3: Drain Punch
move 4: Thunder Wave / Thunder Punch
item: Life Orb
nature: Adamant / Jolly
evs: 252 Atk / 4 SpD / 252 Spe
[SET COMMENTS]
*An event in BW2 gave Jirachi access to Meteor Mash. Combine that with STAB and Serene Grace, and Jirachi can pose to be a pain in the neck by spamming Meteor Mash with a 40% to boost attack
*Ice Punch gives Jirachi coverage against Landorus-T and Gliscor
*Drain Punch restores HP lost from the Life Orb recoil; it also 2HKOs Ferrothorn after an attack boost
*Body Slam is illegal with Meteor Mash, so Thunder Wave is used to slow down faster opponents, like Latios and Terrakion.
*However, Thunder Punch can be used to hit Jellicent, Slowbro, and Skarmory, who takes Jirachi's other attacks with relative ease, but Jirachi needs to be at +1 for the damage output to 2HKO them.
[ADDITIONAL COMMENTS]
*EVs maximize speed and power. Adamant nature with Thunder Wave, Jolly with Thunder Punch
*U-turn can be used to let a teammate come in safely, but you give up the attack boosts you gained from Meteor Mash
*Fire Punch can be used to hit Ferrothorn harder than Drain Punch, but rain is pretty common in OU, and Jirachi will 2HKO Ferrothorn with Drain Punch to begin with
*Jirachi's attack power is a little meager until it gets to +1 or higher; thus, entry hazards can be of use; Ferrothorn is a common choice, but Hippowdon and Tyranitar take a step farther by offering Sandstorm support to wear down most pokemon even farther. Hippowdon can also absorb Thunder Waves for Jirachi, whereas Tyranitar can trap and KO Jellicent.
*An Electric-type pokemon, like Rotom-W or Thundurus-T, is a good partner for Jirachi, as they can handle bulky waters and Skarmory