With the Hoopa forms released, you can use this thread to talk about them. For example: Which item will be the most successful? Where will they end up? Approved by MetalGross and edited to make it readable!
Using this atm: Hoopa-B @ Life Orb Trait: Magician EVs: 4 Atk / 252 SAtk / 252 Spd Hasty Nature (+Spd, -Def) - Substitute - Drain Punch - Gunk Shot - Hyperspace Fury This thing absolutely wrecks everything if you can manage to switch it in, which is actually not too hard with its good SpDef (and VoltTurn support). Obviously the EVs should be switched to 252 Atk when Hyperspace Fury gets fixed, but for now, this set worked wonders for me. Sub is an amazing move as it prevents status and revenge-killing, which are both terrible for Hoopa-B. HF and Drain Punch cover everything but Fairies, which are destroyed by Gunk Shot. Might be suspect worthy at some point; basically something dies when you get this in.
I'm using a set strangely similar to Penspin's: Hoopa-U @ Salac Berry Trait: Magician EVs: 12 HP / 240 SAtk / 252 Spd Hasty nature - Substitute - Focus Punch - Hyperspace Fury - Psyshock While I rarely use Focus Punch, it does have its uses. Hyperspace Fury is currently special, so I'm abusing that to its fullest right now. The EVs will probably get swapped once the move gets tweaked (if I don't just scrap the set). Anyway, purpose: Sub down, blocking status and activating Salac Berry, thus outrunning basically everything with 426 Speed. This also frees up Hoopa's item slot, allowing it to steal an opponent's with Magician. While it can be a gamble, you can really fuck things up should you acquire a Life Orb, and the Leftovers can also come in extremely useful. Probably not the best of what Hoopa-U can do, but damn it's fun to use.