A minor planet (officially known as 2000 EB173) that was discovered in an orbit between Neptune and Pluto in an area known as the 'Kuiper Belt' on March 15 2000 by Charles Baltey at the CIDA Observatory in Merida, Venezuela. Plutino is around 650 kilometres in diameter (approximately one quarter the size of Pluto) and has an orbital period of 243 years.

I've since found out that this is a generic term used for all large objects orbiting in this area, but this is the largest object found so far, and even New Scientist had dubbed it with this name.