Some amazing gurus that come to mind and have not been mentioned:
Ramana Maharshi
“Happiness is your nature. It is not wrong to desire it. What is wrong is seeking it outside when it is inside.”
According to me, the most in-depth and advanced non-duality teacher out there.
He was teaching mostly through silence. When that was not enough for someone, he spoke, pointed to the Self, in many cases advised Self-Inquiry.
Sri Ramakrishna Paramahamsa
"He is born in vain who, having attained the human birth, so difficult to get, does not attempt to realize God in this very life."
Another mind-blowing Indian saint.
This one went the devotional way. I think he is very valuable to study for us, Leo's followers, as there is so little said about bhakti (devotion) on this forum.
Thomas W. Campbell
“The smaller your reality, the more convinced you are that you know everything.”
A living enlightenment teacher. This one is a westerner, a scientist. Amazing teachings, very comprehensive for us logic-based people.
Often compares our reality with a virtual reality or a video game.
Check out his YouTube channel, it is well worth it!
Thích Nhất Hạnh
“For things to reveal themselves to us, we need to be ready to abandon our views about them.”
A Buddhist monk.
His teachings are very simple, poetic and gentle. He is all about mindfulness.
Dalai Lama
“Remember that sometimes not getting what you want is a wonderful stroke of luck.”
I am sure you heard of this one.
Another Buddhist monk.
He is a very wise, old man. Funny and easy to assimilate.
Lao-Tzu
“The truth is not always beautiful, nor beautiful words the truth.”
An ancient Chinese philosopher. I think he is the founder of Taoist philosophy.
His amazing work Tao Te Ching speaks for itself.