My friend Bob Knetzger is a toy inventor. He uses Paper Mate Flair felt-tip pens to sketch out his designs. I bought a dozen for $7 and was reminded why I liked them so much in the 1970s. The lines are smooth and you can vary the line weight by changing the angle between the pen and paper. — MF

Every now and then I try out a new pen but I keep returning to my trusty Pilot G2 Gel pens. Smooth, fine, dark, cheap to lose, and pocketable. YMMV, but they are perfect for me. — KK

Tombow Fudenosuke Brush Pens come in a 2-pack for less than $5. They look like pens, but instead of a nib they have a brush, which allows you to draw lines of varying widths. They’re a lot of fun to use. — MF

For sketching and painting I favor alcohol-based markers. They let you blend colors like a watercolor brush, but with the convenience of a felt marker. The preferred premier markers are the extremely expensive Copics. An inexpensive equivalent for blendable markers with dual tips (fat or point) are Bianyo. I can paint quickly easily in a notebook using a travel set like these 72 Bianyo markers. — KK

These erasable highlighter pens really work as advertised, at least on non-glossy books. The eraser is smooth and by rubbing on the paper, it produces heat which causes the highlight mark to vanish completely. — MF