A couple of times when doing workshops or seminar we have done the Impossible-Possible exercise. Very fun and a great start of a session.
You just split the audience in groups. Use your favourite algorithm to create the groups. Keep groups rather small.
Then let each group describe - in writing and drawings on a piece of A4-paper - a few, say three to five, things that they consider impossible. Give them a few minutes to discuss and write.
Then let each group present one of the impossible things they have found to the whole audience.
Now comes the fun part.
Let them swap papers with "impossibilities". Each group will now have a paper with impossible things made up by another group. So, the challenge is to come up with ways to make these impossible things possible. For every impossible thing they can make possible they earn a point.
Rules? Not really. I have seen people using magic dust and time machines to make impossible things possible. And I have yet not found an audience that wasn't able to transform everything into possibilities.
And of course you should let all groups present their solutions to the audience! Usually lots of laughter and giggling. And some people shouting "cheating!"
After that exercise I get an audience that is very willing to look into possibilities and opportunities. And everything seems very possible for the rest of that day...or life?