This is a flashcard activity which is perfect just for a quick review of recent classes or a lead-in to a classroom game. It's super easy and you can introduce this into any lesson or any level.
Get your students sitting on the floor in the middle of the classroom, with the teacher seated at the front. Get 10-15 big and colourful flashcards of recent vocab you've been studying. Make a pile and hold the flashcards out in front of you.
Cycle through them, one flashcard every 2-3 seconds. The kids need to look at the flashcards constantly. Cycle through the flashcards twice until you get back to the beginning.
After you've cycled through the flashcards twice, rest the pile on your lap and ask the students which words they can remember. Encourage your students to raise their hands and not call out. Keep going and see if they can recall all of the flashcards.
Now tell the class that you are going to play a game. The teacher will say a flashcard and then start scrolling through. The kids have to yell 'STOP!' when you reveal the correct flashcard as you go through. After each time, choose a random flashcard and again the kids urge you to 'STOP!' as you cycle through and when they see the flashcard you've called. A really simple, but effective ESL flashcard activity.