From Bulbapedia, the community-driven Pokémon encyclopedia.
The Fighting Deck is a theme Half Deck from Pokémon Play It! It predominantly focuses on -type Pokémon.
In Pokémon Play It!, it is one of four decks available for the player. Julie always uses the Water Deck against it. She also uses this deck herself against the Water, Fire and Xtra Decks.
In Pokémon Play It! Version 2, this deck appears on all three "Basic Challenge" levels, which are Fighting vs. Water, Water vs. Fighting and Fire vs. Fighting duels, respectively.