Dragoon
Dragoons are Nobodies that mostly appear in Beast's Castle. They are controlled by Xaldin.
They are very spikey, and wield lances. Though most Nobodies are white, Dragoons are mostly purple.
They and their master are, technically, the Kingdom Hearts homage to the Dragoon / Dragon Knight character class of the original Final Fantasy series due to their their usage of spears, being dragon themed (the Nobodies themselves appear as humanoid dragons and Xaldin's spears are dragon shaped as is his strongest attack) and that they use the Jump ability, the job's signature ability. The fact that these Nobodies, plus Xaldin's spears, are purple also stems from the fact that the standard Final Fantasy Dragoon wears purple or dark blue dragon armor or clothing.
Strategy
Dragoons are one of the more powerful Nobodies. They use the jump attack constantly and it can make fighting difficult. Sora can use the jump reaction command to eliminate them more easily. The Jump ability also becomes extremely useful when fighting Xaldin.