BizTalk custom functoids that won't delete
There appears to be a bug in Visual Studio that stops your ability to remove or delete a custom functoid from the BizTalk Mapper toolbox.
This has been causing me no end of grief, as I forgot to rename a functoid when I copied the bulk from a previous one. So I had two listed with the same name.
I deleted from the GAC, the Functoid directory, and searched my registry and hard disk for references. Still, it didn't matter how many times I reset my toolbox, or restarted my computer, it was still listed. Although the functoids list in the toolbox configuration screen didn't list the DLL.
In the end I ran Filemon from the now absorbed Sysinternals, and then reset my toolbox. This pointed at some hidden files in the directory:
%USERPROFILE%\Local Settings\Application Data\Microsoft\VisualStudio8.0
There are four files called toolbox*.tdb. I deleted these (after backing them up, just in case), and reset the toolbox. That solved the issue and the functoids disappeared.