My list is going to be highly idiosyncratic, since I am mainly an autodidact in this area. Sticking to core theory. Biographies, analytical histories, political economy texts etc. are all obviously important too.

Knowns (books I've actually read at least 10% of).

Bold items are books I've actually (gasp!) finished.

1. Robert Nozick, Anarchy, State and Utopia
2. Glenn Tinder, Political Thinking
3. Francis Fukuyama, The End of History and the Last Man
4. Samuel Huntington, The Clash of Civilizations
5. Karl Popper, The Open Society and its Enemies
6. Thomas Hobbes, Leviathan
7. John Stuart Mill, On Liberty
8. Adam Smith, The Wealth of Nations
9. Kautilya, Arthashastra
10. Henry Kissinger, Diplomacy
11. Henry David Thoreau, Walden
12. M. K. Gandhi, The Story of My Experiments with Truth
13. James Scott, Seeing Like a State
14. Noam Chomsky, Manufacturing Consent
15. Thomas Schelling, Arms and Influence
16. Robert Axelrod, The Complexity of Cooperation
17. Plato, The Republic
18. George Lakoff, Moral Politics

Known Unknowns (things I know I ought to read, but don't really want to)

1. Karl Marx, Das Kapital
2. Machiavelli, The Prince
3. Marcus Aurelius, Meditations
4. Adolf Hitler, Mein Kampf
5. Something by Lenin and Mao
6. Stuff by the French Revolution leaders

Unknown Unknowns

?

Political science is an area where I am very uncertain about my own knowledge. I keep suspecting I have huge gaps somewhere that would make real political scientists lynch me. Hence this empty U-U category.