From Bulbapedia, the community-driven Pokémon encyclopedia.
Bill's Ultimate Pokémon Deck is a deck found in the Team Rocket Strategy Guide. The deck is classified as one of the advanced decks in the book, containing more rare cards than the easy-to-build decks. The name and motif of this deck appear to be inspired by Bill and his Pokémon Storage System, considering that a variety of differently typed Pokémon are available, much like how a variety of Pokémon can be stored in the PC box.
Rainbow Energy and Energy Search make it possible to play a deck with as many different types of Pokémon as you like. Each Pokémon in this deck is carefully chosen for its attacks. Except for Psyduck, every Pokémon in the deck has an attack that only costs . Rhyhorn, Zubat, and Kangaskhan also have Resistance to Lightning, Fighting, and Psychic respectively.
This deck is designed to take advantage of the Weaknesses of your opponent's Pokémon. No matter what your opponent's Pokémon have a Weakness to, this deck has it. Use Pokémon Trader to make sure you have the Pokémon you need when you need it. If your opponent plays a Pokémon with no Weakness, use Gust of Wind to switch it with one you can more easily Knock Out.
Your opponent will want to retreat Pokémon that are about to get Knocked Out. Save your Energy Removals to trap a vulnerable Pokémon. Against decks with only one or two types of Pokémon, you'll use the same Pokémon a lot. Save your Potions for those Pokémon.