1.) Science. Mostly the natural sciences like physics, astronomy, geology, and biology but also the social sciences like psychology, sociology, anthropology, and human geography. Some other things I list below are sciences too, but I separate them for convenience. But out of all the sciences, my biggest passions are astrophysics, cosmology, and theoretical physics. Evolutionary biology is another natural science that I have enormous interest in.
2.) Technology and Futurism. Quite simply, I like studying the history and future of technology and its impact on human biological and social evolution. I also like to apply these things hypothetically to potential non-human life forms elsewhere in the universe.
3.) History. Especially through a materialistic lens. I most enjoy general world history, East Asian history, African history, history of war, the history of radical politics, and the history of language.
4.) Philosophy. Mainly metaphysics, epistemology, ethics, politics & economics, logic, aesthetics, and meaning and value. Primary areas of interest for me include philosophy of science, consciousness, objective reality, empiricism and rationalism, moral universalism, theism and atheism, Left-libertarianism, Marxism, Anarchism, and issues surrounding the meaning of life and our place in the cosmos.
5.) Speculative fiction, gaming, and geek culture. Epic/high fantasy and space opera/hard science fiction novels and TV shows and movies. Comic books, superheroes, and some anime/manga. Tabletop gaming, especially RPGs like D&D. Video gaming.
6.) Linguistics. The last year or so I've been on a huge linguistics kick. Phonetics, phonology, morphology, syntax, semantics, pragmatics, writing systems, historical linguistics, sociolinguistics, dialectology, psycholinguistics and neurolinguistics, philology, second language acquisition, general study of and learning how to use world languages, conlanging. I can't get enough of it.
7.) Chess. The most incredible logic puzzle in game form I've ever encountered. I'm big into the chess subculture as well.
8.) Writing and worldbuilding. I love creating worlds and cultures and histories and writing stories set in these worlds.
9.) Reading. I'm always reading something. I mainly read speculative fiction like I mentioned above as well as nonfiction on a variety of topics.
10.) Martial arts. I'm a big martial arts buff and love everything from HBO boxing and the UFC to Bruce Lee and Huo Yuanjia. I especially like studying the history and variety of martial arts around the world as well as the evolution of style and combat philosophy from ancient to contemporary.
11.) Music. Electronic music (Chillstep, unique EDM, House, Synthpop), Blues, Jazz and smooth Jazz, Classical (Western and East Asian), video game music, soft rock, hard rock, 90s pop, hip hop (both intellectual rap and goofy nonsense rap), and political and counter-cultural music are my general favorites. I also play the guitar and love creating my own Blues stuff. I'd love to learn Spanish classical guitar someday.