How to uninstall TrueCrypt?
The TrueCrypt installer is an mpkg file that contains multiple pkg files within it. You can right click the installer in Finder, open package contents and see the pkg files. Essentially, it installs MacFUSE and the TrueCrypt application. If you examine the TrueCrypt mpkg file with a tool like Pacifist, you'd see the list of files it installs and the locations.

TrueCrypt does not come with an uninstaller on OS X. But there are at least two ways to attempt to uninstall it completely:


According to help on the TrueCrypt forum, uninstalling it is a matter of removing MacFuse and the TrueCrypt app (you need to have an account on that forum to see this post):


  sudo /Library/Filesystems/fusefs.fs/Support/uninstall-macfuse-core.sh
  sudo rm -rf /Applications/TrueCrypt.app


OR
Try UninstallPKG to uninstall any application installed with a package (requires OS X 10.8 or later). I haven't used this, and do not know if it will be able to remove MacFUSE and TrueCrypt.


Once you've done this, check the list of files/locations reported by Pacifist, see if any of those are still around and remove them.