Competitive night hike in groups to find ribbons of varying values
Beforehand: Choose an area to hike in. Visit area and tie coloured ribbon on branches and fences etc. Have different colours count towards different values. e.g. red=1, silver =5, gold=10. Obviously you should have lots of low values and not so many high values.
Split into groups and start the night hike searching for the ribbons. Groups need to collect the ribbons and bring back to be counted at the end.