What things take a person out of Islam?

A lot of people ask questions of "is this kufr" or "am I not Muslim." It would be good to have a (semi-)comprehensive list of the things that take a person out of Islam to point to instead of individually answering these questions. Phrased in another way, what things constitute kufr according to Islam? Perhaps, in addition, what are some things people *think* are kufr, but are actually not?