This set utilizes Jirachi's move Charge Beam with its great base 100 SpA and Spe.
Jirachi
[SET]
name: Charge Beam
move 1: Charge Beam
move 2: Flash Cannon
move 3: Hidden Power Fire
move 4: Shadow Ball / Wish
item: Leftovers / Life Orb
nature: Timid / Modest
evs: 4 HP / 252 SpA / 252 Spe
Why this set deserves to be on-site:
-The presence of other Jirachi sets forces a lot of switches, times that Jirachi can set up the Charge Beam on
-Jirachi has perfect neutral coverage with the above listed attacks
Additional Comments:
-Wish can be used for recovery if needed
-Great defenses provide plenty of opportunity for set up
Teammates & Counters:
-Things that remove Special Walls such as Ferrothorn and Blissey are great partners (HP Fire will OHKO Ferrothorn even without a boost)
-Blissey is an excellent counter to Jirachi, as it will switch in and can beat it with Seismic Toss.

Jirachi
[SET]
name: Charge Beam
move 1: Charge Beam
move 2: Flash Cannon
move 3: Hidden Power Fire
move 4: Shadow Ball / Wish
item: Leftovers / Life Orb
nature: Timid / Modest
evs: 4 HP / 252 SpA / 252 Spe
Why this set deserves to be on-site:
-The presence of other Jirachi sets forces a lot of switches, times that Jirachi can set up the Charge Beam on
-Jirachi has perfect neutral coverage with the above listed attacks
Additional Comments:
-Wish can be used for recovery if needed
-Great defenses provide plenty of opportunity for set up
Teammates & Counters:
-Things that remove Special Walls such as Ferrothorn and Blissey are great partners (HP Fire will OHKO Ferrothorn even without a boost)
-Blissey is an excellent counter to Jirachi, as it will switch in and can beat it with Seismic Toss.