Unused type combinations
There are 18 elemental types in the Pokémon games, which means a total of 171 unique combinations are possible. However, even with 1008 Pokémon in the games now, not all type combinations have yet been used. This page lists all the unused type combos in the game. It's fun to think what Pokémon with these types would look like!
Below that we also list some combinations that have been used, but only for either alternate forms, legendary Pokémon or Mega Evolutions. Note that where a type is listed in two sections (e.g. Psychic/Dragon) it means it has been used for both of those categories, but not regular Pokémon.
Also note that new Pokémon are ignored here, so any new type combinations will appear below until the game is officially released.