https://www.youtube.com/watch?v=db-7J5OaSag
RiftSketch is an HTML5 live-coding environment for Virtual Reality.
It lets you code a "sketch" in JavaScript, using ThreeJS, and the world around you changes immediately as you code.
It's quite a niche application since you need to have an Oculus Rift, be a JavaScript programmer and be sufficiently familiar with Three.js but if you meet that criteria it's a surprisingly fun and engaging experience!
If you happen to have a Rift and you want to try it out yourself, download a developer bulid of Firefox or Chrome that includes the WebVR APIs from MozVR or the Chrome dev build share and visit http://brian.peiris.io/RiftSketch/ with your Rift hooked up.