As mentioned earlier, Pachirisu works in mysterious ways. While most Pokemon look to make the most of their items by hoarding them for themselves, a few others look to Trick their items to the opponent in order to cripple them. Pachirisu, however, takes this notion in a direction only a squirrel truly could: up a tree. With Bestow, Pachirisu offers up its item--its proverbial nut--to the opponent. Upon witnessing an act of such generosity, many opponents will refuse to strike such an innocent creature, and will be sent, domesticated by a squirrel, back to their trainers. Of course, Bestow can only work if Pachirisu's opponent isn't already bearing an item (probably not for a gift exchange, unfortunately). To guarantee that Pachirisu gives its gift to its foe, Fling can be used to forcibly chuck the item at the enemy. Of course, Pachirisu can't just stop there. If it brought a gift for one Pokemon, it has to have gifts for them all, right? By utilizing its access to Covet, Pachirisu can perform the act of re-gifting even better than you can when you receive those ugly sweaters from your grandparents at Christmas time.
There are times, however, when even Pachirisu's generosity won't be enough to placate the ferocious beast you may be facing. This is most likely because their trainer is the literal incarnation of the Grinch, pre-heart swelling, and never taught them how to enjoy the act of giving. Or maybe they're mad Pachirisu stole their item? It doesn't matter, though, because Pachirisu will become a ferocious beast of its own, with power rivaling that of a local squirrel that may or may not have rabies. In the event that Pachirisu becomes this uncontrollable monstrosity, Volt Switch can be used to return it to you, thereby calming the beast within. Should Pachirisu fail to return, however, it will likely cut the opponent's life span in half thanks to Super Fang. Alternatively, it might even learn to spit venom and poison them with Toxic. This last scenario is probably only possible if you've dipped your Pachirisu in hazardous waste, for which you should feel really, really bad.
Because Pachirisu is a squirrel at heart, the most genuine item to use is a Lum Berry. This works perfectly alongside Bestow, as Pachirisu's paws are just large enough to hold a Lum Berry, giving the appearance of a helpless beggar, akin to Oliver Twist. Those who prefer to utilize Fling and the more dangerous variants of Pachirisu may want to make it hold a Zap Plate, which will power up Volt Switch and probably tickle the opponent a little when it gets thrown at them. Volt Absorb, as previously lauded, makes Pachirisu the ultimate Electric-type. The EVs are very specific, in order to maximize Pachirisu's effectiveness. 156 HP EVs gives Pachirisu an HP stat of 300, filling it with the souls of shirtless warriors from the movie of the same name. A Timid nature and maximized Speed EVs allow Pachirisu to move as nimbly as its stumpy feet allow, making it more effective at delivering items than either UPS or FedEx. 56 Special Attack EVs allow Pachirisu to OHKO Swanna with Volt Switch even without the Zap Plate, which is important as ducks are the squirrel's only natural enemy. The remaining 44 EVs go into Special Defense, making it slightly harder to cause mental and emotional damage to Pachirisu's tiny brain.