Occasionally, when I haven't been to the local art supply store in a while to replenish my supply of Copics, I find myself grabbing a highlighter for marker work. They tend to have a similar moisture profile to some "art" markers that sit on the drier end of the spectrum, they layer up on top of themselves relatively well, always have a nice chisel tip, and you get to sketch and render in crazy colors. Plus, they're stupid cheap compared with the Copics and Chartpaks of the world. Anyone else dabble in the occasional neon pink and blue sketch?