Thinking back, I was very lucky to be taught by many great teachers throughout my life in many different ways. Of course, some had a teaching style I favoured over others, but all of them took their part in shaping my carrier and personal development.
Nonetheless, there are three teachers who I instantly had to think about, after reading your question, three which stand out greatly from the rest. These three are the ones who eventually inspired me to pursue a career in science. It is very hard to say why their classes had such an impact to my life and what made them so extraordinary. If I had to name something what these three had in common, then that they shared such an unbelievable passion for what they were teaching and for teaching itself. Once you entered their classroom you knew: They love what they were/are doing. They always shared such an enthusiasm for the subject matter they were teaching as well as for inspiring others. Nonetheless, they were also the ones with the highest expectations of their students and encouraged everyone to work on their best level.
Like you I have seen three extraordinary teachers in my life.
Aparesh Bhattacharyya who taught us chemistry in Scottish Church College, Calcutta, Prof. A. K. Sharma who taught us cytogenetics in M. Sc. classes (Calcutta University) and Dr. C. S. Rathore of Indian Institute of Forest Management, Bhopal, Madhya Pradesh. Dr. Rathore gave us a concept of GIS just for five days during a training course.
The lectures of Prof. Sharma ware so good that we never had to go through his notes before our semester examination again.
Yes, many of my teachers "at both school & university levels" have impressed me by their high teaching qualities. I shall give few examples:
1) I was very lucky to have professional teachers of English language at various school classes long time ago. All of them had amiable nature & good personality. One of those teachers is still alive and each time I meet him, tears come to his & mine eyes remembering the good old days.
2) One of my mathematics teachers at school made a very big change in my mathematical abilities by his knowledge & his great sense of humor. This caused me to score the highest mark in my district in 1967.
3) Nearly all of my teachers at postgraduate level in Great Britain were excellent in chemistry possessing in-depth knowledge, great characters, kindness, and friendliness at their old ages. They made me "love" chemistry (especially the practical side of it).
Yes, my supervisor Retd. Prof. S.C. Sharma, Department of Botany, Govt. Dungar College, Bikaner, Rajasthan. He has expertise in taxonomy and define in very simple language; He always say that "taxonomy is like a mathematical subject, if you learn terminology, you know 50% of plant identification". I am very lucky that I have done my Ph. D. under his guidance.