1999 KW4
Wow! We haven't had a Freak Wave thread for a long time. There are more Killer Asteroid threads and should be another on KW4.
"KW4, the astronomers say, is actually a pair of light, porous clusters of rubble that circle each other as they orbit from a point closer to the Sun than Mercury and then outward - occasionally passing very close to Earth along the way. The bodies were discovered in 1999, but not known to be binary until they were observed in May 2001, when they came to within 3 million miles of Earth - this asteroid's closest pass until 2036."
--spaceflightnow.com
1999 KW4