There are some skills in the game that are not sold on the open market. Some skills were part of eve at some point, but were phased out. Others were never seeded into the market. Such skills are Salvage Drone Operation, Mobile Factory Operation, Mobile Refinery Operation, Astronautic Engineering etc. There are some unseeded science skills as well. Most of these are collectors items, and do affect gameplay.

One interesting rare skillbook is nanite control. This decreases the side-effects of boosters, and only drops from rare npc pirate rats.