One of my favourite activities for older, more advanced learners is to give each student a bunch of cards with different opinions on. If the opinion matches the student's own then they hang on to the card. If they don't agree with it then they must get rid of it by finding a student who does share that opinion and giving them the card. Usually, you get lots of interesting sharing of opinions and students get to know each other a little.
At the end of the class, go around the group and see what opinion cards each student is holding. Lots more discussions will probably spark up along the way.
There's a set of opinion cards
on my website which you can download and print.