Screwdrivers & Hex Keys
Those fasteners that aren't hex heads usually have one of several differently shaped recesses in the head. Years ago, 3 or 4 screwdrivers would cover just about everything, but now screw heads can be straight, Phillips, Torx or square drive. A good quality interchangeable tip screwdriver keeps down the toolbox clutter, compared to individual tools. Similarly, a folding set of Allen wrenches gives you the size you need, always at hand.