This is a good, quick and fun way to revise vocabulary.
Have a blank page on the IWB or whiteboard, students come up and draw a picture to do with the topic you are doing, others shout out or are selected to guess what it is.
It helps if you write down the word on a post-it that the student has to draw or you can just whisper it to them as long as no-one in the front row has crazy hearing abilities!
You could also do this in pairs with mini whiteboards or scraps of paper too…
The worse the drawings, the more fun it gets!