Wireless Network Watcher - scans your wireless network and displays the list of all computers and devices that are currently connected to your network.
Avira Home Gaurd - Avira Home Guard is a free home network scanner app that helps secure the smart home, detects all devices connected to your Wi-Fi and tests your internet speed.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
Advanced IP Scanner - Advanced IP Scanner shows all network devices, gives you access to shared folders, and can even remotely switch computers off. Download it Free.
MiTec Network Scanner - A free multi-threaded ICMP, Port, IP, NetBIOS, ActiveDirectory and SNMP scanner with many advanced features.