Speed dating is great for adults.

Also: Alibi, where you present a class with a hypothetical crime, and divide the class into sets of pairs. Each pair must come up with a convincing alibi and then one pair goes outside while the other gets 'interrogated' by a the rest of the class being 'detectives'.. If their stories don't match, then they're guilty (I always ended up with a whole class of guilty people).

If I had a class of 40, I'd modify it so that the pairs were in turn paired with Ss changing roles between detective and suspect. This does work best with a talktative class, I wouldn't try it with a class you struggle to get language out of.

The class I did this with pulled out every line from bad American detective movies they'd ever heard. My favourite line was "this is harrasment, you're victimising me."

For kids, my 4-9-year-olds can't get enough musical chairs.

Counting game for 9 - 12 year olds: every fifth number is exchanged with 'my name is....', or 'days of the week' or 'months of the year'.  All class must stand up, when there is a mistake in counting, student must: 'zuo xia!'

Usually, student with the best grades in the class is the last standing.

After few students sit down, all sitting students became judges, and when they spot mistake, they all scream: 'zuo xia, zuo xia....'

Hangman: I let students do the game. Student must give a clue to the Class with  short English description of the guessing word.

I show the rules of Hangman with few examples. Last description is: 'He is the man with short hair. He is present in the Classroom at the moment'. 

Guessing word on the board is 'lao wai'. 

I hang them on this one, but I cannot leave classroom at the end. I am still in, when teacher of the next class arrives.