From Bulbapedia, the community-driven Pokémon encyclopedia.
This is a list of Pokémon by their catch rate, from the highest rate to the lowest. This means that the Pokémon which are easiest to capture are listed first, and the Pokémon that are the hardest to capture are listed last.
In Pokémon Omega Ruby and Alpha Sapphire, the catch rates of Kyogre, Groudon, Dialga, Palkia, Reshiram, and Zekrom, the version mascots made obtainable in those games that did not already have a catch rate of 3, were changed to 3, while the catch rate of Rayquaza was raised from 3 to 45.
Generation I held items
In Pokémon Yellow, four Pokémon will have different held items than their Red/Blue counterparts when traded to Generation II. The starter Pikachu's "catch rate" value is set to 163 (as opposed to 190), which causes it to hold a Light Ball when traded over. A wild Kadabra's catch rate value is set to 96 upon capture (as opposed to 100), which gives it a TwistedSpoon when traded over. A wild Dragonair's catch rate value is set to 27 upon capture (as opposed to 45), which gives it a Protein when traded over. Finally, a wild Dragonite's catch rate value is set to 9 upon capture (as opposed to 45), which gives it an Antidote when traded over. However, wild Dragonite cannot normally be obtained in Pokémon Yellow.
List of Pokémon