I like to start class with an opening activity that promotes discussion and gets lots of students to participate. Questions in the format of "Which One Doesn't Belong?" allow a lot of student voices to be heard. It also gives a voice to students who think outside the box. There are many different ways to answer these questions. The important part is to provide a logical reason for the item you've selected. I'm consistently impressed with the creativity of students. The WODB question below combines two of my favourite things... math and pencils!
You can find lots of great examples of this type of question on the wodb.ca website, or check out the @WODBMath twitter feed.