Merlin 1D Vacuum (M1DVac) engine - the core of the new Falcon 9 v1.1 & Falcon Heavy upper stage.
Besides the explosive hydroformed fabrication, which is faster and much cheaper than machining & plating the thrust chamber, it's simpler and has almost 28% more thrust that the Merlin 1C Vacuum in current use.
Falcon 9 v1.1, M1D (sea level) and M1DVac will make their maiden flight from the new SpaceX pad at Vandenberg Air Force Base's Space Launch Complex 4 East (SLC-4E) in Q1 2013.
Fabrication: explosive hydroforming
Thrust: 80 metric tonnes (176,370 lb/f)