Old Greek and Roman Philosophers:
-Aristotles
-Socrates
-Philo
-Plato
Midevil Philosophers and Renainsance:
-Spinoza
-Joannes Scottus Eriugena
-Friedrich Schelling
Modern philosophers:
-Friedrich Nietzsche
-Kant
-Fernando Savater
-Theo de Boer
Muslim Philosophers:
-The Moetazili thinkers, although theologists, were very philosophical
-Aboe bakr Al-Razi [250AH]
-Ibn Khaldun
-Ibn Rushd (Averoes)
-Muhammed Iqbal
-G.A. Parwez
-Allama Mashriqi
There are more, but these I read a lot.