My approach to the first day of class is to keep it simple. I think too much is made of the first day. I'm not saying it's unimportant, I just think one doesn't have to be cute or clever on the first day. There's so much in the teaching and learning literature about the first day of class. I think the second day of class is much more important (more on that another time). On the first day my goal is to show that I'm an energetic and enthusiastic professor. My plan for the first day of my SOC 101 class this year is to develop a definition and description of sociology. I find that students who are new to sociology already have a sense of what sociology is. I just have to draw it out of them and work with what they give me. I simply say "Give me a word or phrase that has to do with sociology. It's okay if you're not sure." That usually produces plenty of content to establish a solid definition of sociology and the topics of interest to sociologists. It also allows me to differentiate sociology from psychology. It's a basic exercise that involves students. That allows me to show students that I want them to contribute to class. If I'm already encouraging them to speak on the first day, then obviously I'm expecting (and encouraging) them to speak during every class. That's my goal, rather than spend time on introductions and icebreakers. It's not that I hate icebreakers, I just figure they've had enough icebreakers during orientation and in other classes.
That's pretty much how I keep it simple on the first day. I introduce everyone to sociology, go over the syllabus, encourage them to visit me during office hours, and tell them to be ready for a fun and interesting course!
PS if you're wondering how to teach the incoming first-year cohort, here are two essential things you need to know to prepare to teach 18-year-olds in 2017: