Tied with Grass, Rock types have the most weaknesses of any type, with five. Additionally, double weaknesses among Rock types are very common.
Since Generation IV, the Special Defense of a Rock-type Pokémon is increased by 50% during a sandstorm, in addition to being immune to the damage caused by it.
Rock-type Pokémon, on average, have the lowest Speed of all Pokémon and of fully evolved Pokémon.
In particular, Rock pairs well with Ground, since very few Pokémon naturally resist this combination. Most Rock-types can learn Earthquake to this end. The biggest drawback of Rock-type moves is the large percentage of moves which have less than 100% accuracy.
Disclamer: Rarity of an individual Pokemon can and does vary depending on the spawn location. In the table below the lowest rarity is presented. Please check individual routes for more information on the rarity of your desired Pokemon.
Disclamer 2: All Pokemon names and locations contain a hyperlink to their pages. Links have been colored black for design purposes. Please note that not all pages are of quality or even exist, work in progress.