Make a small spray paint stencil or vinyl sticker that represents your crew, or inspires people to think differently, and put them around your town or natural areas in subtle, cleverly inconspicuous locations.
Explore your area with Alltrails, or a similar app, finding new hiking or biking trails.
Urban exploration: creep through abandoned buildings, climb fire escapes to reach the rooftops, use catwalks under bridges to cross roads and rivers, scurry through large water drain pipes and abandoned steam tunnels.
Start a lucid dreaming competition with your friends, and share your experiences every morning. As you all develop more dreaming skills, you can share them with each other, and slowly become the masters of your dreams.
Come up with scavenger hunts that guide people into the coolest, hidden areas of your town, using clever clues, and share them online, similar to geocaching.
Pick up rubbish off the ground, one area at a time.
If it doesn't exist publically in your country, get equipment to either test air or water quality at several spots around your community, and then share them online through posts, or by hosting an Ushahidi map. Encourage others to chip in.
Get your gang to volunteer together to help homeless, elderly or disabled people once or twice a month. You will both bond with your buds and gain new perspectives from the people you work with.
Arrange spontaneous dance parties in public with little flash mobs made up of your mates. Try to get strangers to join in on the fun. Disperse after one song, so you don't get in trouble.
Learn to identify the 10 most common trees in your area, then the 10 most common flowers, the 10 most common weeds, the 10 most common birds and the 10 most common insects.
Explore local theater, try to find weird niche performances at churches, swingers clubs, primary schools, corporate retreats, futurist festivals, government events, and street corners. Make sure to cheer loudly and throw flowers.