Some third-party apps you install on your Mac might nest custom panes within OS X's System Preferences, mostly those distributed outside the Mac App Store due to sandboxing requirements. Uninstalling such an app automatically removes the underlying pane from System Preferences but not always, leaving you scratching your head.
Case in point: Tuxera's MacFUSE, a dynamically loadable kernel extension.
I needed to mount files to an NTFS-formatted drive the other day so I installed MacFUSE. After removing the app a few days later using its own uninstaller, I noticed its pane in System Preferences was left intact. Should that happen to you, here's how you can safely remove stubborn System Preferences panes from your Mac.