Attached is a basic PPT for a lower ability class in KS3.
It goes through number facts and a movie at the end of each round.
Pupils are placed into groups - no more than 4 per group as people start to disengage, you can give each pupil a job to ensure all are working. All should have working out paper. This is a great way to encourage group mathematical discussion and pupils working together.
4 rounds - 5 questions each and the best team with the most points at the end wins a maths piece of equipment. Q4 is the same on all rounds as it was something my class found difficult, some serious misconceptions around adding unlike terms in maths.