Mashup games are always fun. Those built upon FourSquare have an extra layer of enjoyment, because they're tied to the real world. In the case of City Warfare, players use various water weaponry to soak other FourSquare users.
Created in 2006, Big Art Mob's original purpose was to accompany the Channel 4 show, 'Big Art Project'; the goal being to create the UK's first comprehensive map of street art. The site is now being re-launched along with iPhone and iPad applications, inviting users to upload and map public art anywhere in the world.