Travel 100 metres without being seen.
Put on a performance for a CCTV controller. You could improvise a short play, show off a dance routine or hold a full blown talent show.
Go guerrilla and change a place with plants.
Go for a walk; bring back your favourite memory and then recreate it.
Collect 26 photos of the letters A-Z in different places.
Carry out a dog survey in two different parks.
Paint a stone red. Leave it somewhere and then come back at a later date to see if you can find it again.
Plant some beautiful flowers or start a community garden to make a neglected place more beautiful.
Explore your local area looking for signs and words that command you to do things. If you find one, do what it says.
Post paper blog entries on your street.