Tunnelblick - free software for OpenVPN on OS X and macOS
OpenVPN - OpenVPN - The Open Source VPN
WireGuard - Fast, Modern, Secure VPN Tunnel
Hamachi - Hamachi is a VPN service scaled to the unique needs of business owners.
Pritunl Client - Simple OpenVPN Client and GUI. Additional integration available when connecting to a Pritunl server.
Freelan - You are in control. Why would you trust a closed, proprietary software with your most-sensitive data ? Freelan is open-source and completely free. You know everything about its internals and its source-code.