This is a list of tools I use or have used. They are in no certain order and are listed for anyone else looking for useful tools.
Wireshark is a network protocol analyzer is a life saver when it comes to troubleshooting network traffic.
iPerf / JPerf
When pinging between two devices doesn’t give you the complete story, using iPerf3 / JPerf (GUI based interface) allows you to truly measure the network performance between two devices.
Nmap / Zenmap