Master ball

Master Ball
This is the most effective type of Poke Ball (with a 100% catch rate), and consequently the rarest as well. It was originally manufactured by Silph CO. in Saffron City, but only a few were produced before Team Rocket tried to steal them. Since then they have been discontinued. From then on, the few remaining prototypes were only given to accomplished Pokemon researchers. Because of this, only one can be found normally in each game (although it can be won in each generation after the first; it is the grand prize for the Lucky Number show, Lilycove City's Lottery, and at the Jubilife TV station, respectively. The player could sell it in Generation II (for $0), but no Poke Mart in the following generations will accept it.