I, of course, am an avid preserver, and therefore we have approximately one million mason jars in our condo. If you believe Pinterest, there are one million uses for them. However, I don't see the value in painting them or turning them into cutesy votive holders or what have you. I use them for canning and storing dry goods, and that's about it.
But there is one clever use that I am a fond of. Did you know that the diameter of a regular-mouth mason jar is the exact same diameter and has the same screw-on track as most standard blenders? When I learned of this, I was all MIND = BLOWN.
Just take the blade and gasket off the bottom of your blender, and prep your ingredients.
Blade goes on. Screw it onto the base.
And, blend. Salad dressing has never been easier. Screw on the lid and ring to store, and all you have to wash is the blade and gasket.
Amended: I neglected to mention that you should not do this with hot foods, as the expansion of steam will create pressure, and potentially cause the jar to explode, or at best cause the gasket to seal too tightly. Also, though I demonstrated this with a half-pint jar, pint jars work best as they have more headroom.