I like set theory, model theory and logic. Classification theory for infinitary logic, infinitary combinatorics. Topics in Set Theory, a Part III course in the Mathematics Tripos at the University of Cambridge: http://www.maths.cam.ac.uk/postgrad/mathiii/guidetocourses/2015-2016/logic/TopicsinSetTheory.pdf

Moderators note: Oren Kolman passed away in 2015. See https://ests.wordpress.com/2015/12/17/oren-kolman-1959-2015/