What do you think the absolute most devestating pitch thrown in the major leagues is? I'm talking, a pitch that you can know is coming, where its coming, and still miss.
I'd give Trevor Hoffman's changeup the nod, hes throws 84mph and is still able to have an allstar season because this pitch is so nasty. He throws it with great control, masks it perfectly, and of course gets devestating sinking action on it.
A close number two however, would be Joel Zumaya's fastball. He is ridiculous, he throws his 2 seam fastball at 100 mph and gets significant movement on it. He is consistently over triple digits with it, and while occasionally someone will tag it, 98% of the time hitters are in trouble.