Rubbing alcohol can be a surprisingly effect artistic tool. It is a wonderful and cost effective blender for alcohol inks and alcohol ink based markers. Additionally, alcohol breaks down the wax coating from colored pencils, allowing artist to blend colored pencil pigments as though they are paint. This creates the ability to makes smooth gradients that may otherwise take a lot of time and materials to create.
Alcohol can also be used with the mediums mentioned above to create texture. Dripping alcohol onto alcohol ink eats through the pigments, creating a starburst like effect. Alcohol can similarly be used in a spray bottle to cover more surface area; this is excellent for distressing surfaces. If using alcohol with water based ink, such as that found in Sharpies, you can create a watercolor effect by painting or spraying a color blocked pattern.
Last but not least, alcohol is an excellent cleaning tool. Alcohol dissolves polymer clay off of tools and off of skin. It can also dissolve tough to remove mediums, like varnish, from brushes. Alcohol will not work well to remove oil based mediums from your tools, but it can remove excess oil from the surface you were working on.