I play a very, very, simple form of RISK with the afterclass students, split into four teams.
Draw a basic world map on the board and separate into 20-30 countries. Each team chooses 3 countries to start with. Then ask questions, relevant to students' level, using a fastest finger approach. The first team that answers correctly gets the chance to 'invade' a connected country using rock, paper, scissors.
I play it so the answers have to be 100% grammatically correct, this increases the competition, whilst focusing the students to exactly what they're getting wrong.
'I want to be singer' > 'I want to be a singer'
Obviously this depends on the natural enthusiasm and level of your students, but you'll be surprised how well this works.