The flat head screwdriver is probably one of the most common and versatile tools. With its flat, bladed end, the flat head screwdriver is specifically designed to loosen and tighten screws that have a linear notch on the top. The flat head screwdriver is not only cheap (costing anywhere from $3 to $10), but the versatility of this tool goes far beyond just loosening and tightening screws. This nifty tool can also be used to accomplish a myriad of tasks, such as prying and scraping or even notching or holding. Flat head screwdrivers come in a range of sizes, from minute for fixing the screws in your glasses, to much larger sizes for more industrial work. They can be long and thin to reach into small spaces or short and thick for durability and strength.
Avoid using your flat head screwdriver for tasks that don't include loosening or tightening screws because they're prone to break when used incorrectly.