Not really tool but like others, toothpicks, wooden coffee stirrers, q-tips. All of these can often be had for free or picked up for next to nothing on the clearance table. The wife knows to keep all the pudding and yogurt cups the grandkids eat up. I have two bins in the shop. One for small containers with lids and one for small containers without lids. The non-lids are everything from Pepto-Bismol cups to Yogurt cups. The lidded ones are old Rx containers, food cups with lids and so forth. Over the years I have gathered so many that I do not hesitate to use them.
Cheap tools that get used a lot include a $1 scraper that I threw in with a Grizzly order; wish I would got a few.
These fat boy pencils. I have bunches of carpenters pencils but these work better for me. I also use
these mechanical pencils in 9mm, and 5mm. I got a couple of 2 size sets for about $10 each many years ago. The 5mm work with Incra steel rules (the ones with the little holes drilled everywhere. I notice a lot of folks on You Tube and the Fine Woodworking videos using them. I'm sure they didn't get the idea from me. They probably just found that the GraphGear ticks a lot of boxes for the woodworker just as I did.
Glue Bot glue dispensers. Very reasonably priced. I picked up a 3 pack at a woodworking show in 2005. I'm still using the first one. I have the smaller size too.
Oh,
2" spring clamps from Home Depot. Very well made for a buck each. I sometimes use them for something in the yard like holding on a tarp. If they get forgotten or destroyed I just pick up a couple the next time I'm at the store.
Lee Valley right-to-left cabinetmakers tape measure. This is the one in my apron pocket, magnetically stuck to the tablesaw fence, and at the bench. Inexpensive and they all match my steel rules and each other.