It is difficult to choose a one blog post among all. But I feel there are few type of post which changed my thought process are blogs written by experts in the field. I love reading how they think about something whether its a computer program or science or cooking or hobby they have.
Also more than just a blog I love reading author, if I like something about blog I go deep read their other blogs as well and if I feel the guy is worth following I just start reading their blogs and I do read repetitively.