Superscan is a free Windows-only closed-source TCP/UDP port scanner by Foundstone (now part of McAfee). It includes a variety of additional networking tools such as ping, traceroute, HTTP HEAD, and whois. Some functionality has been crippled by restrictions imposed by Microsoft in Windows XP SP2 and newer releases. This tool is not really maintained (the latest release was in 2004).
For downloads and more information,
visit the Superscan homepage.
I have been using this utility for years. It's my favorite port scan utility and extremely useful for finding IP's/hostnames on local subnets. I don't use it for scanning the internet, but when tracking down the IP address of WAP's, routers, printers, etc it is wonderfully useful. After discovering said hosts a + sign indicates an expandable list of available ports per host. For printers/routers/WAPs a right click context menu enables to to quickly open that IP in a webpage over port 80 for configuration. 5 stars!