as a plenary, pictionary of the key words for the lesson. i teach a little maths as well, and easily the funniest lesson ever was revising types of graphs using twister (of the form 'right hand on the graph that you use to compare two lots of information' or 'left foot on the line graph that is drawn incorrectly' etc - using other students as referees). clearly this needs a lot of room, some preparation in drawing out the board, a smallish class and a HUGE amount of supervision! very funny, though, and could be easily transported to almost any topic.
When I was at school (seems a painfully long time ago now ;-) one of our science teachers did a class debate on heat transfer. He had half of us argue for Lavoiser's caloric theory and the other argue for particle theory. It was brilliant - I want to do the lesson with my year 8s but it was so long ago now I can't remember exactly what resources he used. Is this a lesson that anyone else has ever heard of/used, or do you think it was just made up by that particular teacher? This is a discussion of heat transfer rather than combustion. So, the two ideas are: