The new MBE4000 series truck engine is pretty sweet. Built of course by Mercedes-Benz. Power output ranges from 350 - 450 HP. The really impressive thing is that it's at 100% of its torque at 1000 rpms. That's some quick turbo response. Speaking of turbos, it can be equipped with a turbo brake system that produces 600 braking horsepower.

http://www.americanfreightliner.com/mbe4000.htm

and then there's the MBE900...

http://www.detroitdiesel.com/Public/ddc_prod/s900.asp