Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Fingbox - Fingbox home network security device helps you keep your internet safe and secure, allows you to monitor your household digitally and improve your home Wi-Fi experience.
Eusing Free IP Scanner - Free IP Scanner: a very fast IP scanner and port scanner.
MiTec Network Scanner - A free multi-threaded ICMP, Port, IP, NetBIOS, ActiveDirectory and SNMP scanner with many advanced features.
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
MASSCAN - This is the fastest Internet port scanner.