From Bulbapedia, the community-driven Pokémon encyclopedia.
Rain of Tears is a type deck found in the Gym Challenge Strategy Guide. The deck is classified as one of the "hard-core" decks in the book, containing more rare cards than the easy-to-build decks. It is inspired by the Raindance archetype.
The "Rain of Tears" deck uses Misty's Tears to jump-start the Blastoise Rain Dance engine. Misty's Tears allows you to get Water Energy out of your deck, while Blastoise's Rain Dance power lets you attach as much Water Energy as you can to your Water Pokémon in a turn. You can quickly power up Blastoise's Hydro Pump attack to do 60 damage every turn.
When you're playing this deck, you want to get Blastoise into play fast, so you can start pouring Water Energy onto the table. Use Pokémon Trader to get Blastoise or Wartortle (whichever one you need), and use Pokémon Breeder to speed up the evolution process. Master Ball also gives you the chance to find Blastoise or any other Pokémon you might need. Use Misty's Horsea and Misty's Seel to slow your opponent down (using their Ink Spurt and Mirage attacks) until you can get Blastoise on the table and powered up.