Final answer:
TeamViewer is the recommended remote support tool for Gigantic Life Insurance's varied and geographically dispersed environment due to its compatibility with domain and non-domain joined Windows 10 PCs, and its ability to function without direct network connectivity.
Step-by-step explanation:
In choosing a remote support tool for Gigantic Life Insurance's help desk that supports users across multiple physical locations, the goal is to find a tool that can easily connect to both domain-joined and non-domain-joined Windows 10 computers, without the need for direct network connectivity. For this situation, TeamViewer would be the most suitable option because it does not require the computers to be on the same network or domain, it works through firewalls and NAT proxies, and it is platform-independent, making it flexible for a range of situations that the help desk might encounter. Tools like Remote Desktop Connection would not work for non-domain joined computers without direct network access. While VNC Viewer and AnyDesk are also viable options, TeamViewer's established reputation for high security with end-to-end encryption, ease of use, and robust feature set for both IT support and non-technical users makes it a strong candidate for standardization. Additionally, TeamViewer offers features such as session recordings, file transfer, and mobile device support which can further aid in providing comprehensive support to users.