The scheduler activity allows your students to sign up for a time slot. This can be used to arrange for office hours, control access to equipment or for any purpose where you need to limit when your students do something.
The Moodle Questionnaire is a survey activity. It allows teachers to create a wide range of questions to get student feedback. The goals of the Questionnaire module are quite different from those of the Moodle Lesson or Quiz activities. With Questionnaire you do not test or assess the student. Instead you gather data. Unlike the Choice activity, you can gather more information than a single question can provide.
The attendance activity allows an instructor to record student attendance in the course sessions. One attendance activity lets you track attendance for the entire semester (so you only need one). Students will be allowed to see only their own attendance.