Andy Grove, Bob Noyce and Gordon Moore of Intel. Moore's law guided not only Intel but helped fuel the growth of the entire IT industry for decades.
Andy Grove co-taught a class at Stanford on Technology Strategy (he was still CEO of Intel at the time). It was definitely one of the most enjoyable classes I took during business school. Andy didn't put up with bullshit. If you didn't know what you were talking about, he cut you off. That was one class I made sure I was prepared for!
I once invited Andy Grove to a charity golf tournament at Stanford. He replied (via email) "golf bores me to tears."