Riddles/Logical Puzzles.
The teacher describes situations to students which seem illogical. Students discuss the problems to try and 'solve' them. I find this is best done as a teacher-centred activity with the teacher responding to all the student questions and leading them, very slightly, towards the solution if they are struggling.

Riddles/Logical Puzzles Memory Game.
This activity was sent in to us by Ian Haley teaching in Osaka, Japan. If students cannot solve the puzzle once they've shared all the information they can each ask the teacher questions but the teacher can only answer yes or no.

Guess the sentence.
Fun speaking activity in which students attempt to slip, unnoticed into their conversations, pre-selected sentences. Can be used to target specific structures and their uses.

Using Poetry.
Interesting activity sent in by Bill George teaching in Germany.