Well, I don't know if any of them "changed" my direction, but gave me either a deep interest or understanding of their subjects. I remember them all, although not necessarily their names:
English teacher, second year of high school. Made me see the beauty of good writing and prose, and how to put my imagination into words. He didn't last long in a very traditional school environment, unfortunately - his teaching methods were "off syllabus", and he left a year later after having a nervous breakdown. He left his mark, though, and I always think of him when writing.
Biology teacher, Mrs. Noble, last two years of high school. Besides being a MILF (well, at least to some of us pre-pubescent boys in an all boys school), she gave me a thorough understanding of Biology in a gentle encouraging way. She also brought out my artistic side. I still have my notebooks from those classes, and I marvel at the intricately detailed drawings of amoebas, plants, insects, etc. that I did.
Maths teacher, technical college (Electronics). I HATED maths at school, and had a mediocre pass in it at the end of the day. He introduced me to calculus, and his teaching style sort of brought all my previous maths training together and then added LSD. It was literally a mindf*ck - like suddenly solving a Rubik's cube and knowing exactly how you did it. Whether the the half-jack of brandy he used to drink at lunchtime at the strip club across the road had anything to do with it, I'll never know, but SOMETHING worked - I scored 100% for all maths related subjects for the last 3 of the four semesters, and never looked back.
Applied Maths lecturer, Dr. Hahn, second year university (Engineering degree). The subject says it all. Took the staid knowledge and made it work. He taught me that theoretical maths was a tool to be used, not like a sledgehammer but rather a scalpel with an ever-changing blade.
Control Engineering, Dr. Martin Braae, 3rd and final years of my degree. He brought literally everything together for me. Sure, given the subject matter and level of instruction, this was, I suppose, the desired outcome, but the way he did it was exceptional. He had a passion for practical implementation, and had stocked up his labs with the most uncanny contraptions for us to dissect. I did my thesis under his guidance, and won the national prize for the best thesis that year.
Astronomy, Prof. Don Kurtz. I did a filler course in my final year in Astronomy, as I had always had an interest in it. It was tough - you could not miss a single class, and it was at a very inopportune time for me, considering I was doing final year, and spent most of my time away from campus in the second half of the year (40 km away) doing my thesis. I had to travel in every day for those last 6 months for one 2 hour lecture just after lunchtime. I never regretted it. Don was a master lecturer, and I looked forward to every class, which is something I cannot say truthfully for all of the above. I achieved the highest mark in the class, and it was easy doing it. Considering that I hated physics at Uni, and this was physics intensive, that was quite an achievement on his part.
Don came the closest to me making a career change. If I had had the opportunity to study for just one more year, I would have jumped at the chance to finish my degree in Astronomy (besides the Engineering degree). Hell, another year would have allowed me to finish off my Computer Science degree as well!
Unfortunately, my bursar pulled me out of student life before I could do so. This is, to this day, one of my biggest regrets.