ClickOnce doesn't require admin privileges to install software. Each program is installed on a per-user basis under the user's profile. So it doesn't need admin rights to write to C:\Program Files. I'm pretty sure this is how Chrome works as well.

As for installing COM components, you can install COM components on a per-user basis as well. The registry keys are installed under HKCU rather than HKLM, so again you don't need admin access.

I program .NET client applications for my day job and we use ClickOnce to deploy our software. The software doesn't require admin access to install or use, and we register a COM component for integration with Excel and it all works just fine.