Some people may be more aware of relatively popular ancient philosophers. This graphic shows the diversity of modern philosophical thought.
Some of my favorites include:
Merleau-Ponty – described the phenomenon of facial recognition, even across species.
Focault – wrote some very interesting post-Freudian analyses of sexuality, particularly heteronormativity and its effect on society’s views of homosexuality and gender roles.
Dostoyevsky – many people don’t know he was an philosopher. He reads very similar to Nietzsche, in my opinion. A fantastic introduction to the philosophy of Dostoyevsky is Notes from the Underground.
Nietzsche – his writings often use science and the scientific method to obtain philosophical ideas. The genealogy of morality is one of the best introductory books to his style and thought.
Of course, remember that the purpose of philosophy is not to define morality, or even give answers about valid questions (such as why a variety of organisms can recognize faces, or why gender roles exist). Philosophy is an exercise in thought. Don’t be afraid to read something you initially disagree with – read it and fully understand what you disagree with and how tenable that position is.