Pokémon attack type coverage
This little app lets you select up to 4 types corresponding to the attacking moves you've taught (or plan to teach) to a Pokémon. It then tells you how effective those types are at tackling every known Pokémon.
For example, if your Pokémon has one Normal attack and one Fighting attack you might cover a few Pokémon, but you would have nothing that can hit Ghost types. Add a Dark move in there and you cover that and more besides.
Not Very Effective