Although they don't contain a registry editor, the Windows Sysinternals tools from Microsoft have some great ones like Process Explorer (task manager replacement), Process monitor (shows all real-time Registry activity as well), ZoomIt (great for screen drawing during presentations) and so on. Written by Azure's CTO way before the cloud existed :)
Instead of process explorer, I highly recommend people to use Process Hacker[0]. It's open source, contains a lot of information missing from process explorer, and has a much cleaner user interface.
Another great one is WinObjEx64[1], which allows exploring the NT namespace.