Piranha

• It is still weak (rated around 2000 on schach.de and on ICC).
• Piranha doesn't come with a GUI, but supports the UCI protocol. A fine free interface is Arena.
• I offer it for download here: piranha.zip (version 0.5, 564 KB). Windows only!
• You can read more about Piranha in the readme file (which is also contained in the zip).