It's not much fun, but it's the only activity which comes to mind. How about a game of request and excuse? Divide the class in groups and give them all the same list of 12 or 15 requests :
I want you to translate this letter into Portuguese. / Can you put these documents away? / Go and find out what time the meeting starts. / Can you go and get a birthday present for your sister? / Can you feed the cat this evening?
The groups have to find a reason to say no using the target language :
I don't know how to speak Portuguese / I don't know where to put them / I don't know who to ask / I don't know where to go /I don't know how to use the tin opener./
At the end the groups read out their answers. They get one point for a correct answer, but three for one which is not only correct but which no other group has thought of.
Well, I did say it wasn't brilliant ....
