iClip

For macOS. Shareware (try first, pay later), $14.99.

iClip manages clippings of text, images and files. It optionally automatically records the contents of the clipboard every time you copy something. I am the main developer of iClip.

See the iClip site for more information and download.

Prefs Editor

For macOS. Free.

Lets you edit the preferences of any application. Like the 'defaults' command in Terminal.app, but easier to use.

See the Prefs Editor page for more information and download.

Find Empty Folders

For macOS. Free.

This little tool finds folders that have no files inside, apart from other empty folders invisible files such as .DS_Store, and gives you the option to delete them.

What's Open

For macOS. Free.

Lists open files on all volumes, for any user. Helps figuring who which apps prevent a volume from being ejected or unmounted.

See the What's Open page for more information and download.

iBored

For macOS, Windows, Linux. Free.

The internet-enabled Block Oriented Editor is a tool to view and edit disk sectors and related files.

See the iBored page for more information and download.

Launch Services

For macOS. Free.

A tool to work with the Mac's registry. Lets you browse the entire UTI tree and look up apps that open a specific file extension or match a bundle ID.

See the Launch Services page for more information and download.

ShowClipboards

For macOS. Free.

A tool for developers to analyse and test the clipboard / pasteboard.

SSDP / UPnP Browser

For macOS. Free with Source Code.

SSDP is a method (protocol) for finding devices on local networks, including UPnP devices. It's similar to Bonjour (Zeroconf) but more popular outside the Apple world.

You can download the built app at https://github.com/tempelmann/SSDP-Browser/releases.

This app also comes with source code (Objective-C), being a nice example on how to use NSOutlineView, NSTreeController and Bindings. It opens in Xcode 8 and later.