Every artist has go-to tools for different creative endeavors. Some of those tools end up being invaluable! I've made a list of some of the items I use in my day to day work in comics.
Portable Drawing Board
This board has been amazing! When we were moving out to Portland I grabbed one of these and I was able to set up whenever we stopped over in a hotel for the night. It also helps in a pinch when I can't get to my office to work. I can just set it up on the dinner table for an hour or so and then fold it back down to tuck away until later.
Zebra Brush Pens
I've mentioned this before, but I love these brush pens! The Zebra brush pen made be fall in love with traditional inking again after a long break from the art form. These pens can give you a beautifully thin line if you use a delicate touch. Generally, I use these for my broad lines and Sakura Microns for the super fine details.
Ever since my husband gave me his drafting ruler, I have never used another. There's this cool roller on the underside that makes parallel lines SO easy. (Functions as a compass, horizontal ruler, straightedge, protractor, circle template and angle template multipurpose drawing instrument that lets you measure in inches and centimeter.)