This set is for VGC doubles.
King Louie (Oranguru)@ Sitrus Berry / Mental Herb
Relaxed | Inner Focus
252 HP / 128 Def / 132 SpD
0IVs in Speed
- Trick Room
Oranguru is a Trick Room + Instruct bot. That's all you'll really be using it for. Sitrus Berry restores a good chunk of HP to Oranguru and is preferable to Leftovers in VGC. Alternatively, I also suggest Mental Herb to stop Taunt. Taunt is a popular way of shutting down Trick Room, and a Mental Herb guarantees that TR gets set up (unless it is Knocked Off first, but the you have bigger problems than being Taunted). I would run Sitrus Berry if you have Fake Out support, and Mental Herb if you do not.
The EVs allow it to survive a Modest Bug Buzz from Vikavolt (however, not if it holds a Life Orb). On the physical side, it also survives Knock Off from max Attack Muk and Flare Blitz from max Attack Thick Club Marowak. 0IVs in Speed make it as slow as possible in Trick Room.
The moveset is pretty straightforward. Trick Room is Trick Room. Protect is a staple in VGC unless you're running a Choice item or Assault Vest. Instruct is Oranguru's niche. Attacking twice in one turn is awesome, especially when paired with heavy hitters like Muk, Marowak, Torkoal, and Scizor. Two Sun-powered Heat Waves? Two Technician Bug Bites? Two Bonemerangs? Oranguru can provide. Psychic means Oranguru's not total Taunt bait and lets it battle Crobat, its biggest counter, if it catches it on the switch.
In most situations Inner Focus is the best ability for Oranguru. It prevents Fake Out from stopping your Trick Room from going up. However, if you're confident in your ability to get Trick Room up and you really want to spam Instruct Earthquake, Telepathy does have its uses.
Good teammates for Oranguru are A) those who help it set up TR and B) those who benefit from Instruct and Trick Room. Hariyama is a great partner for Oranguru because it has Fake Out, low speed, and powerful Close Combat/Bullet Punches. Shiinotic can also help it set up with Spotlight. I suppose if you're feeling real gutsy you can use Rage Powder Parasect. As for Pokémon that benefit from Instruct/TR, the ones I listed above are probably the best.
Oranguru is not without it's problems. Common Pokémon like Muk and Marowak are dangerous because of sheer damage output and how well they can make Trick Room work against you. Crobat is also a huge problem. It usually carries Taunt to stop Trick Room, has Inner Focus to stop Fake Out support, can be quite bulky, has Brave Bird/Cross Poison to KO Rage Powder support, and U-Turn to slap Oranguru in the face and leave, probably to be replaced by something that can KO Oranguru. Doubling up on Crobat or Taunting it first with something like Sableye or Klefki is the best way to handle it.