Imagine an open virtual world where people could build and design their own apartments, buildings, structures, etc. and are able to invite their friends over to view their creation in first-person and hang out. Kind of a mixture of Omegle, The Sims and AutoCAD. You could also collaborate with other creative users to help contribute to your creations in ways such as restructuring/reediting your creation or giving ideas/feedback. VR-support would be an awesome touch too!