"What is "THAT" Pokemon that you need as fast you can on your team?"

As the title states, What pokemon must you find/have on your team as fast as possible? It doesnt matter where you are in the game you MUST find this pokemon to satisfy your team. The pokemon can be the weakest link on your team but you dont care.For me Personally it has to go to Abra or Dieno. Despite the pokeballs spent to catch Abra, I must find one (I even spent like 5-8 hours trying to find/catch a shiny Abra) via /r/pokemon http://bit.ly/2VnNmQj