For those discussing Jirachi leads, I find that TrickScarfer with Thunder-Wave works effectively in the Suspect tier at the moment. Magnezone doesn't pop up quite as much, and Jirachi is able to cripple any number of leads, save Heatran. It's nothing terribly original, but it's effective.
Pokemon Name:Jirachi
Moveset Name: Alternative Lead
Move 1: Trick
Move 2: Thunder-Wave
Move 3: Iron Head
Move 4: Stealth Rocks/U-Turn
Item: Choice Scarf
Nature(s): Adamant
EVs: 144 HP / 252 Atk / 112 Spd
The idea here is to couple Jirachi with Heatran (or another Flash Fire Pokemon), and a ghost, preferably Rotom form, and a few Levitators like Latias that can spam destruction.
Trick against most leads is a wise choice; Swampert, Metagross, Gliscor, and Hippowdon all hate to be Tricked a Scarf, if they attack with Earthquake, or setup Rocks. If Rocks go up, Thunder-Wave comes next. If they attack with Earthquake, then you have a free switch in for one of your Levitating Pokemon (U-Turn on Flygon, Specs Latias, and Gyarados are good choices).
When faced with a Fire type attack, you have a couple of options. Trick Azelf, it will either be locked into Flamethrower/Fire Blast, which means Heatran switches in for free, or it will be stuck in Stealth Rocks. Stay in against Infernape and Trick; if he Fake Outs, then switch to Latias/Gyarados, or other Counter on the second turn. If he goes straight to his Fire move, you'll likely Trick a Focus Sash onto yourself, meaning you hang on, while Infernape is now a free switch in for Heatran. Speaking of Heatran, they give Jirachi a lot of trouble in the lead spot. Having a few Pokemon to Counter Heatran, like Latias who can Recover off the damage, or a Scarf Heatran of your own to switch into Fire attacks is recommended.
Stealth Rocks vs. U-Turn in the final slot is simply up to team preference. The sweepers I pair with Jirachi, Gyarados, Heatran, and Latias all apperciate SR being down, but U-Turn helps scout moves, and escape from the dreaded Magnezone.
The EVs given are to outpace Jolly 252 Speed Aerodactyl leads you may face, and take them out with Iron Head. It may still be a wise choice to Trick Aerodactyl though, if your team can afford Rocks on the field. You can definitely run a more defensive spread, with an Impish nature, and EVs into Defense, but Jirachi does serve as a decent Pokemon mid-late game to spread paralysis and Flinch everything to death.