OpenVPN - OpenVPN - The Open Source VPN
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.
ZeroTier - Extremely simple P2P Encrypted VPN
Lets VPN - Lets VPN app comes up with features to assist you in enjoying high-speed internet by simply connecting with a multi-national line internet without having to worry about the security of your smart devices.
SigaVPN - SigaVPN is a VPN service that lets you reroute your PC to a different IP address and surf the web anonymously.