As suggested by a friend, today I'm going to write about one of my favourite artists, and certainly one of the least conventional around. Edgar Mueller (or Edgar Müller), whose art you may well have seen, paints his art onto pavements, in such a way that when viewed from a particular angle, they seem three-dimensional. It's usually known as "perspective pavement art" or a variant. Because of this, I find his works very intriguing. It's amazing that something, done right, can completely trick your mind.[youtube=http://www.youtube.com/watch?v=3SNYtd0Ayt0]
The other unconventional aspect to his work is that it's done with non-permanent paint. He will spend days on a stunning piece of artwork, then a single rainstorm will wash it all away into nothingness. Rain has, on at least one occasion, ruined a piece of work prior to its completion - he will now generally cover the art up with a tarpaulin during storms so it can at least be completed.
Mueller's website can be located here. To view pictures of his perspective pavement art, click here (this includes some of his works along with progressive pictures to give you an idea as to how he goes about his artwork), or search his name on Google Images. If you haven't seen it already, I would highly recommend it.