Ditto
@ Sitrus Berry/Leftovers
EV's: Whatever, he's Ditto.
- Transform
Everyones use Ditto with Choice Scarf to outspeed it's "clon", but... it makes Ditto almost or completely useless if you're not copying a sweeper, then here we have a most balanced Ditto, making him able of forcing a switch to those sweepers who copy, making them to think Ditto will always outspeed them, and at the same time, makes him able to counterstall any wall, and makes him able to use a powerful surprise factor changing from one move to other on the worst moment for your opponent, or even if they somehow predict it, Ditto is copying you! He'll always leave a mark on any countender.
Sitrus Berry works better if what do you want with it is to create the illusion that him's using Choice Scarf, because the opponent will don't know what items is carrying Ditto until they outspeed him (if that ever happens, you still have 50% chance to outspeed them, or if they switched their sweeper, you'll almost always outspeed) or they damage Ditto below the half. Also, Sitrus Berry can allow Ditto to create a Substitute on emergency circunstance, like the opponent leave him with 1-24% of HP, then Sitrus Berry will health you up and you'll set your substitute! Giving you sometimes an oportunnity to evade a status, or to set up and sweep or stall.
Leafovers by other hand skips the "Look at me, I'll outspeed you!" bluff, and comes to a more balanced Ditto, Ditto can be able to stall or to sweep for more time with it, or to at least make him able to switch-in more offen if Stealth Rock/Spikes/Toxic Spikes are on the field.
This change of item worked really well for me, at least, the surprise factor is good, but being able to use the 4 complete moveset of the enemy is sometimes great, and more when the unique way to win against some sweepers is setting up like they can.
Of course, without Choice Scarf he's less able to Revenge Kill, and more against newbies who will just try to "outspeed you" all the time, but then here comes a smart play with it, you're copying something who can K.O itself on one turn? Have a plan B then. You're really needing to stop sweeps or sweep with Ditto? You'll only win the 50% of time, have a Plan B and C if you're unlucky or don't wanna take the risk. You opponent is smart enough to know if Ditto usually runs Choice Scarf or not? If he does, then surprise him, if you think he doesn't, then don't over predict it.