The Snap-On F50CSA driver handle. It's a 3/8" drive driver handle with the socket cap in the head so it can be used as an extension. I bought one off the Snap-On truck back in like 1994 or so and it's been my favorite hand tool ever since. Sadly they don't make this model anymore, so if I ever lose mine then I'm stuffed. Well, maybe you could find a used one on Ebay or whatever, but it would probably cost out the yazoo.
https://thumbs.worthpoint.com/zoom/images1/1/0311/29/snap-f5...