"Always on Top" Keyholes

As I was moving an "always on top" window around my screen the other day,
trying to see what was underneath it, I realized that I'd identified an
"Alway on Top" (AOT) keyhole.  However, the program I was using (Windows
Task Manager) has a setting that controls whether the window is always on
top, so it's not really a keyhole.  (If users can make the keyhole go away,
it might be bad default behavior, but it's not a keyhole.)

My copy of ACDSee 5 has an AOT Keyhole in its help system, in that the help
window insists on being on top of all other ACDSee 5 windows, but windows
for other applications may be on top of all ACDSee 5 windows, so this is an
intra-application AOT keyhole.  Does anybody know of an intra-application
AOT keyhole, i.e., an application that forces a window to be on top of all
other windows, including those from other applications, and where users
cannot disable this behavior?

There is some kind of relationship between AOT keyholes and modal dialog
keyholes, but I'm not sure what it is.  Perhaps a modal dialog is just a
common manifetation of an AOT keyhole.  Comments?

Thanks,

Scott