Choose at least 4 opposing theories/theorists/themes/ideas/approaches etc and allocate one to each  group of students.  Each group has to research their theory/approach etc and also research the opposing groups theories etc. The aim is to provide support for their own theory and evidence to criticise other groups’ theories.  Each group has one person in the ‘hot air balloon’ and the debate commences to decide which theory is the most worthy of remaining in the balloon. Only one person is allowed in the balloon at the end. Work out a scoring system such as 1 point for a valid contribution but 1 point deducted for someone criticising your ideas. To avoid a free for all, allow each group one minute to speak without interruption, then allow opposing groups to challenge.