Another bit of fun for the ESL classroom!
This one works particularly well for a Students Vs. Teacher type activity. The teacher asks a student a question (relating to that lessons vocabulary or grammar or as a review), if they answer correctly they are safe. If they answer incorrectly the teacher can flush (by simply pressing the space bar) one of the students down the toilet! Once all the students are swimming merrily in the sewer, the teacher has won.
There are only 9 students in the game so, if you have a larger class than 9, you may want to make it so that two wrong answers flushes one student down the toilet.