3/16" - Expansion card retention screws for IBM PC, XT and probably the AT, XT/286 and Portable, Expansion card retention screws for the Tandy 1000/A/HD/SX. Drive mount and system board retention screws for IBM PC & XT, probably others.
7/32" - IBM Model M Keyboard screws, probably Unicomp Keyboards as well. Needs a long barrel bit to fit inside the three of the four holes for the screws.
1/4"- External case screws for the IBM PC, XT and probably the AT, XT/286 and Portable, Internal case screws for Tandy 1000s. IBM Model F PC and probably AT screws. System board screws for Tandy 1000s. Floppy disk drive mounting screws for IBM PCjr.
Later, more generic PC cases can still use the 1/4" and 3/16" bits, even though they have Phillips-screw heads, as they are still using hex heads. Sometimes in-between bits like 5mm and 6mm can also come in handy, the former especially when trying to screw in port standoffs.