Well in terms of end user support i am afraid there is no way around Teamviewer. It simply works everywhere, sometimes in a creepy way for admins cause they thought their desktops would be safe behind firewalls.
You can choose between different modules (each with own logo and branding). The Host version is aimed for remote controlling to login without any interaction. The Quick Support module, hence the name. is for support without the need for installation. It can be added to your software. the full-blown Teamviewer Client Software is for everything.
I strongly suggest not to use any of these 3rd party software on mission-critical systems or servers.