This list is focused on exams published 2000-2010. These make for great bathroom/beach reading. Enjoy!
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1. PrepTest 35 (October 2001), Passage 4 – Ronald Dworkin and Legal Positivism vs. Moralism (p234 in Next 10)
2. PrepTest 49 (June 2006), Passage 4 – Maize
3. PrepTest 50 (October 2006), Passage 4 – Riddled Basins of Attraction
4. PrepTest 55 (October 2008), Passage 3 – Maxine Kingston and the Chinese talk-story
5. PrepTest 59 (December 2009), Passage 3 – Isamu Noguchi and Sculpture
Also, here are some Difficult LSAT Logical Reasoning Questions and the 10 Hardest Logic Games.