It strikes me that shoving the Grim Reaper into any orifice is the ultimate defiance, that grand "fuck you" to death that characterises much of the human race. Death becomes life-affirming; its image transformed into something to be used and controlled. Even the phrase 'sex toy' belittles death. Lo, the Grim Reaper as dildo; we have made it our toy, we have conquered it.
No longer fear death! Stick it up your pussy instead!
...There's something in that about people who deliberately go out to get infected with HIV, surely. I think at that point it stops being life-affirming again.
The actual object that inspired this bizarre chain of thought:
http://www.blowfish.com/catalog/toys/symbolic_dildos.html