On Linux systems, you have directory trees like /usr/local or /opt where you can put "custom-installed" applications which don't have a package in your distribution and, thus, do not fit nicely into your distribution's FHS.
On Windows, where do you put applications which do not provide an installer, and, thus, do not split themselves nicely into C:\Program Files (x86) and C:\ProgramData? Is there a well-established convention?
Background: Many small tools (e.g. the sysinternals tools) or Unix-ported applications (e.g. emacs) do not provide a Windows installer but rather a zip file with the instruction to "just extract it anywhere and start the exe file". Now, I could create an arbitrary top-level directory, e.g. C:\Tools, but, being pedantic, I'd like it to have the "right" name. Is there some consensus or does everyone invent his/her own convention for this type of application?