1. Tokyo Tribe 2 - Goosh Goosh
This is right on the border of most disturbing, while not being in the category of the previously mentioned videos.
2. School Days - The Boat Cruise Ending
The ending is infamous, with the final moments being filled with bloody death and a head in a bag.
3. Nisenmonogatari : Toothbrush Incest
It's impossible to talk about this scene without grasping your face and letting out an exasperated sigh that says: "Maybe every human should be dead."