Here is a short list that will not break either your bank or your back. Most of this will fit in a decent sized tool box, with the exception of those cards.

Light Control

For shaping, shielding, reflecting, filling, removing, and otherwise pushing light around to make it do what you want it to do.

Cards These are the workhorses in the studio, in many sizes, depending on your subject matter. White for general fill; smooth or pebbled silver for pumping in a hard hilight; Black to deepen an unlit area, especially in a small studio with light colored walls.

Cinefoil This is heavy duty black aluminum foil that can be cut, torn, or folded into the shape you need. Plain old aluminum foil can also be handy- alone or wrapped around a plain card to turn it into a silver card.

Fabric Black felt or velvet is the ultimate light sucker. Use it to elimintae unwanted loight or reflections, or when you need that ultimate black background. A small piece can be folded into your toolbox and takes the place of a much larger card. White fabric can also replace a card for some uses, but not all, especially if you are using it to put a hilight on a shiny object. White fabric is more useful as...

Diffusion Material Fabric, tracing paper, drafting mylar, specialty diffusion products available from Roscoe, Lee, and others. In sizes proportional to the subject you are working with.

Filters Also from Roscoe or Lee.

Mechanical Helpers

These help you do what needs to be done. Keep them handy so you don't have to run out for them, causing you to waste your time and pull your hair.

A-Clamps Sizes from small to large, useful for everything from holding cards to adjusting the fit of clothing.

Clothes Pins Cheap, infinitely useful.

Paper Clips Wire style can be bent into any shape; Clamp style can be used as a small A-clamp.

Straight and Push Pins Lots of uses that you will recognize when you don't have any. Push pins are especially useful in still life work to keep backgrounds from sliding around while you are positioning your subject.

Tape White artists; Black Light Tight; drafting (less sticky) and masking (more sticky); Scotch celophane; Double Sided; Gaffer's.

Tacky Wax For keeping small items in place, or making them do things that they would not ordinarily do.

Kneeded Eraser In addition to its use to clean up smudges on props and backgrounds, it can be molded to any thickness to use as a shim for propping up small items.

Cleaning Stuff

Photoshop or not, cleanliness is next to godliness on a set.

Brushes Artists brushes for still life cleaning. Hair and make-up for people.

Q-Tips For cleaning small spots, applying oil and grease.

Windex Cleans anything that's water soluble and then some.

Mineral Spirits or Rubber Cement Thinner Removes tape glue and other smutz that Windex won't touch.

Jewelers Cloth, Polishing Cloth Two grades of fine abrasive embedded in a soft cloth. For removing tarniish and polishing metal.

Paper Towels For bigger messes.

Other Handy Tools

You will need these, though I can't say exactly when or why.
Scissors Sizes from small to large, useful for everything from holding cards to adjusting the fit of clothing.

Tweezers Various sizes, especially if you are working on small still life.

Level For leveling you camera. Also critical for leveling a set that will show liquid... before it is all set up.

Pliers, Needle Nose Lots of uses, from pulling staples to opening bottles.

X-Acto Knife, Blades For fine cutting and trimming.

Utility Knife For rough slashing of cards and foam core.

Screw Drivers, Philips and StraightNot only do things break, sometimes they just need to be taken apart.