Acrylic WiFi Free is a free-for-personal-use wifi scanner which runs on Windows 7 and later.
The program identifies local wireless access points and devices and displays a table listing their details: SSID, MAC Address, Vendor, type, RSSI, channel, 802.11 (a/ b/ g/ n/ ac), security details (WEP/ WPA/ WPA2/ WPS), and when they were first and last seen.
In addition, a Signal Strength chart plots the strength of each signal over time, while "2.4GHz APs" and "5GHz APs" charts graphically show their channel usage.
A built-in Connectivity module can run brute-force testing on your chosen network against a sample dictionary of common passwords.
There's also an optional Monitor Mode which uses Acrylic's own driver to monitor network packets and may help you identify hidden networks.
A $47.99 (lifetime license) professional version takes the product further by displaying more information, generating reports, capturing data via airpcap and being able to work with pcap files, too.
The interface is clunky in places and documentation isn't great, but Acrylic WiFi Free looks good and works as advertised.