Kingda Ka

At 128 MPH--which it reaches in 3.5 seconds out of the loading area no less--Kingda Ka is the world's fastest coaster. That's 8 mph faster than Cedar Point's similar Top Thrill Dragster, which has been downgraded to the world's second-fastest roller coaster in 2005. Kingda Ka climbs a top-hat tower at 90 degrees. In this case, the apex of the tower reaches a staggering 456 feet.We're talking over 45 stories in the air.The trains crest the tower and plummet 418 feet straight down the other side before entering into a 270-degree vertical spiral.

http://themeparks.about.com/od/sixflagsparks/a/KingdaAnnounce.htm
http://www.sixflags.com/parks/greatadventure/Rides/KingdaKa.html

Kingda Ka Stats

Type of coaster : Hydraulic launch rocket coaster
Height : 456 feet (tallest in the world in 2005)
Top speed : 128 mph (fastest in the world in 2005)
Location : Six Flags Great Adventure in Jackson, New Jersey
Coaster elements: 456-foot tall top hat tower, with 90-degree ascent and descent, 129-foot second hill designed to provide free-floating airtime.