Well for about 3-4 hrs straight I calc'ed up my Bulky Ono's set. I looked through all the current OU pokemon only, and only factoring in a few of the new counters it has. Over the course of all the calcs, Scizor came out every time as the top check, as well as forry, Natto, and Skarmory(to an extent). With my bulky set being tweaked all around, Jirachi wont be able to effectively counter it without it possibly staying it and only continuing to boost its damage (bar the substitute T-Wave set).
Ononokusu @Leftovers/Haban Berry/Lum Berry
Adamant/Jolly Nature
200 HP/44 Atk/60 Def/204 Spe (ev's need to be tweaked if using Jolly)
Ability: Mold Breaker
-Dragon Dance
-Outrage/Dragon Claw
-Earthquake
-Taunt
The item will depend on what your more afraid of really: Scarfchomp, not enough bulk, and status effects. the atk EV's are enough for Ono to OHKO ScarfRachi after 1 DD, and OHKO SD Lucario without any boost. A scizor bullet punch wont do as much damage (48.4-57.2%), but still needs to be feared because you wont be able to KO it. It's better to just switch out if it shows up, and counter it respectively. As I've already mentioned before, Jirachi becomes a possible set fodder, except for the sub T-wave set. The Wish Calm Mind set can't do enough damage to you, allowing you to easily get 2 DD's. The scarfed set will either be setup bait, or hax you to hell. Here's a quick outcome chart for ScarfRachi:
This is if Jirachi is switched in to attempt to check Ono after it's already got a +1 one form the switch:
1. Jirachi Iron Heads- Iron Head will do 32.6-38.7% which will only 4HKO with Leftovers, and possibly 3HKO without. The scary portion of this is the flinch rate, which would be at 60% do to serene grace. IMO, I'd personally risk another DD here since I'd still have a 40% chance to not be flinched. After that 2nd DD, Jirachi is slower then Ono, and dies immediately to the EQ. If you dont have another check for it after Jirachi, you can pretty much expect your team to lose some more pokes possibly.
2. Jirachi Ice Punches- Not as scary as Iron Head Hax. It'll deal around 41.1-48.7% to this Ono. If it doesn't freeze you then Ono gets a free DD, Kill, and possible sweep afterwards.
Other reliables checks are: Natto & Forry (both of which who take laughable damage from EQ, and resist stabs), Skarmory (although brave bird can't reliably 2HKO this set, but it can still take it out before it becomes to strong. it has to beware of a +2 outrage though), Flygon (those that dont hold Haban Berry or at +2), ScarfChomp (same as Flygon), Mamoswine, Shaymin (LO sweeper only), and Machamp (who'll almost be kO'ed, but will OHKO with one Dynamic Punch).
If anything, I'll be trying this set out along with the scarfed. With the right teammates though, Ono will be ferocious. Possible partners can range from all different prespects. Heatran, and Sazando, for one, are both powerful teammates that can deal with his common checks. Shanderra with ST can trap possible checks, and place them in unfavorable situations or simply KO them. Some bulky waters can give him problems, but having a poke that deals with the waters can make his sweeping easier as well.
This thing has so many viable teammates, and a good bit of sets that are quite variable to make prediction somewhat hard against this thing.
