I'd like to keep the Jirachi hype train going: this thing belongs in B+.
More and more, I find this little punk to be an amazing teammate. Rocks, U-Turn, Wish, Body Slam, bulk, hax: Rachi has it all. Its Body Slam comes with a 60% para chance, making it the perfect lure to bring Landorus-T, Heatran, Greninja, Kartana, or Torn-T down to an awful speed level. Because so few of its checks resist BS Para + Iron Head, it almost always has a play that can advance a win condition: either you rock into a check, Wish into a check and then run and heal a teammate, Body Slam/Toxic to spread status, U-Turn if you got it, or just go for some IH flinches.
Jirachi's niche as a SpDef support mon has been widening for a while now. While it used to only see usage to counter Lele, people have found that it can do a lot of other things due to its good bulk. M-Latios has a 0.4% chance to 2HKO it from full with EQ. Prot Gren's HP Fire is a 3HKO. M-Zam's Shadow Ball is a 3HKO. Bulu cannot beat any of its sets, Celesteela 4HKO's with Flame, Pex can't Poison stall it (and hates Para), Ice-Z Kyu-B 4HKO's it.. The list of things it checks goes on and on, from M-Diancie to Torn-T to Chansey or Clefable. And keep in mind, each of these mons that it checks have to be wary on the swap to keep their teammate from taking paralysis. While Jirachi isn't a one-man show, still losing hard to Heatran, Ash-Gren, and Lando (among others), as a defensive stopgap it's very useful.
Despite the rise of Rotom-W, Tapu Koko, Zapdos, and Magnezone, Rachi is one of those mons that, like I said, has the move slots to play around. Toxic + Wish/Protect can annoy all of them - especially Magnezone who will get PP stalled. U-Turn lets it keep up momentum against unfavorable switch ins as well. And that's all just talking one set - scarf has its merits as well, including Trick, Healing Wish, and hax-based cleanup. Time to boost this man.