Depending on the style and type of case the good old 4-in-1 screwdriver with two sizes of phillips head and two flat head screwdriver tips is all that has even seen a need here. The smaller of the two phillips head tips seems to be the universal fit there. Board fasteners, drive screws, case fan fasteners, etc. along with a thin pair of pliers to grab any that fall in the case and even some transparent tape to hold a screw on the end of the phillips when first reaching in depending on the frame of the case usually goes smooth.