I always find it most helpful to keep in mind that Matter is all about changing the properties of inorganic materials (just like Life for organisms and Forces for energy). You can think of Matter like this can simplify it. Just take a substance and give it properties it doesn't normally have or transform it into a different substance. Anyway, here's some fun stuff:

-Change spray paint so crystals grow out of the paint. The crystals can then be shattered like glass for instant caltrops!

-Transmute the thread of your clothes into a light and durable metal, like Kevlar....