What are some essentials that artists should carry around with them and in their pencil case?

I was told by C.F. Payne to draw with whatever you like drawing with. If you love drawing with blue BIC pens...use a blue BIC pen. There is nothing that is a must have. Don't get caught up in technicalities...just create!What are some essentials that artists should carry around with them and in their pencil case?
A range of graphite pencils, some charcoal pencils and sticks, of course, are needed. A kneeded eraser, a pink pearl eraser, and pencil tipped eraser are great tools for not only making corrections but are also sometimes important drawing tools in themselves. A brush that can remove eraser crumbs yet is soft enough to not disturb the drawing. Some sharp razor blades and sandpaper for shaping pencil and charcoal tips. Smudging sticks, and soft rags are great for shading. I actually have a lot of stuff in mine and sometimes can't remember why I have it in there. I have had a thimble for almost 20 years and I am not sure what I used it for.What are some essentials that artists should carry around with them and in their pencil case?
A couple of soft lead pencils, a sharpener, kneaded eraser and a couple of Sharpie markers for inking. (I carry two each of fine point and extra fine point)





That's just the basic necessities for sketching in the field. The drawing pad could be as large as 12 by 18, or as small as my five by seven sketchbook. I rarely, (but sometimes do) bring a large, 18 by 20 sketch pad and sketch board.





I almost never do any coloring in the field, but when I do, I bring a box of a dozen or so color pencils. But, when color accuracy is VERY important, I take a digital photo.





But, with my minimal sketching supplies and small sketchbook, I can go, virtually, anywhere without having to lug around a bunch of art supplies. For real, paid work, I bring the sketches and phots back to my studio and work in air conditioned comfort, with ALL my media at hand and within easy reach.
Ive come across a couple of books on works done with colored pencil. I was amazed by what can be accomplished with colored pencils. Check it out at the library or Amazon. The books were titled: The Best of Colored Pencil. They featured works done by many different artists.
pencils, lead (if mechanical) or pencil sharpener (for wood), extra BIG eraser, white out for pens, whipes for hands (after smearing for effects) and i know i'm forgetting something.