Sagittarius A* (the black hole at the centre of the Milky Way) is spinning really fast.
(Note: Although black holes are given a spin value a that has a value that ranges from 0 to 1, the possible top speed a black hole can spin at is proportional to its mass.
The Order of Time
At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds
A Brief History of Time
A Universe from Nothing
The Greatest Story Ever Told—So Far
The Elegant Universe
