I don’t have many specific toolkits, and I certainly don’t move in the lofty organizational circles of people posting in the systainer section of the Festool Owner’s Group, but I do have a basic kit for electrical work around the house that lives in its own canvas bag. It’s very convenient to pull the bag out when I have a quick job like switching out lights.
The basic kit includes wire cutters/strippers, a current tester, three-prong outlet tester, wire caps, adjustable screwdriver, and needlenose pliers. For more ambitious work like new circuits or outlets, the kit gets supplemented (metal fish tape, fiberglass fishing rods, a key hole saw, drill bit extensions, etc.), but the basic kit covers a lot of ground and isn’t so expensive that I have money tied up in something that doesn’t get used often.