There are a number of types I don't really care about. But my least favorite are probably Ghost, Poison, and Psychic. I've just never been a fan. While I don't like other types, there is enough pokemon in them that I like to omit them here.
Ghost - Until Kalos, I didn't really like any ghost type pokemon. But all of the Kalos Ghost types I've loved. As well as Decidueye. Ceruledge also came along and has been a favorite.
Poison - Aside from the Nidos, Dragalge, and Nihilego, there aren't many I like. And I only like Nihilego because of the Shiny.
Psychic - Latis, Ralts line, and Hatterene are really the only ones I like. I used to like the Reuniclus line, loved it in Unova games, but I have barely used it at all and I guess I've lost interest in it over timer.