One tool I find helpful and easy to use is Today's Meet. I would use this in my Geometry class for open-ended questions that create discussion and different views that they can discuss. In my sample, I asked the question, "is a rhombus more similar or different than a square?"
I also like the idea of using Poll Everywhere in the classroom. I have often polled the students using the Activotes, but this is a much more efficient form of polling. In this example, I surveyed the students on a preferred method for solving systems of equations.