Canada, US, EU, Mexico, Japan are the only currencies of places I am likely to revisit.
From my visit to UK I had about £14 in coins that I sold to a friend. I still have small amounts in coins from Romania, Macedonia, Albania, Thailand, Malaysia, and Indonesia. I was hoping to encounter a coin donation bin in an airport on the way home or at least a Unicef donation box on a flight (which I haven't seen in years). That's how I got rid of other coins.