NOTLD '68 and Sleepaway Camp are the two most shocking endings for me (on the list). It was a hard decision but ended up voting for Sleepaway Camp. Not only was that ending shocking, it was down right disturbing as well.
"Let it be known sons and daughters, that Satan was an acid-head. Drink from his cup, plegde yourselves and together we'll all freak out!" - Horace Bones (I Drink Your Blood)