Truthfully I don't keep up to date with the latest "shocking" thing on the Internet. Most of the things mentioned here are pretty old. Truthfully though I have to say that "funnel girl" is the one I keep coming back to when I think of stuff that made me go "WTF".
2 girls 1 cup is nasty, but pretty much relies on someone being unaware of the whole scat fetish thing. Absolutly disgusting, but not all that in the scheme of things. Understand that in the truest sense "geeks" were people who entertained in sideshows who would eat anything (including feces and the like) to shock, disgust, and amaze the audience. Part of the gimmick being a "will you eat that?" type thing with people offering money to see if they would do it (and inevitably they would). Once your aware of such things, 2 girls 1 cup is easy enough to put into perspective even if it's not something many people are going to watch for entertainment (and especially erotic entertainment). Truthfully things like "Swap.avi" have gone a lot further than that ever did.
3 guys 1 hammer is an act of violence and cruelty, but sticks out mostly because your seeing what transpired, rather than just hearing about it, of witnesses the aftermath. It's sort of like a violent horror movie except real.
Ultimate Muscle Roller Legend (the video shown here) is mostly disturbing because it seems really, really, gay (which it is for the most part) but then again a lot of people don't get the joke or what it's pointing fun at. You pretty much need to know what "Vocaloid" is, but more specifically about the specific anime mascot girls involved, and the obsessive fandom about them.
http://en.wikipedia.org/wiki/Vocaloid
What your looking at is pretty much someone busting on the Vocaloid fanbase, by pretty much having a Vocaloid run off the road by an equally obnoxious depiction of a gay porn star. I can't remember the guy's name, but apparently he's supposed to have become popular to a ridiculous degree in Japan. I think the idea was to sort of make people who were into sexualizing Vocaloid girls feel sort of uncomfortable, and poke fun at the entire
obssessive fan base. When you know who the gay guy is and why he was probably used, and who the girl is, the intent of the video (beyond general wierdness) makes a little more sense. Or at least it becomes a bit less disturbing.
At any rate, what "gets" people is differant. See, where scat is a major turn off for me personally, the idea doesn't offend me to the point where simply mentioning it or putting up something scat related is going to get a major "OMG" reaction. I mean the idea just became a lot less shocking to me a long time ago. The thing about "Funnel Girl" is what happens specifically. Basically you've got this guy chained underneath a potty chair with a funnel reaching down into his mouth. Some girl walks in, sits down, and unloads a stream of diahrhea down the funnel into his mouth. The guy goes absolutly ballistic, struggling and trying to escape, but there is no end or easy out since she can't even see that I don't believe. Now whether this was some "2-girls 1 cup" type submissive scat fantasy gone horribly wrong for the guy involved, the girl torturing the guy for her benefit, an unusual punishment and video humiliation for not paying a debt, or some clip from a porn movie (2 girls 1 cup was from a trailer for a scat movie allegedly) is unknown. The whole out of control nature of the situation along with it possibly being non-consentual put it over the top for me. I haven't researched it heavily but one prevelent rumor was that it was actually footage from a police interrogation (the country varies) where allegedly the police hired prostitutes and sex workers to do things like this. The idea being that it's not immediatly lethal, and if you watch that happen to someone, your probably going to do anything not to be next (or to prevent it from happening again).
At any rate with all the rambling that's not the newest, but so far it's "tops" with me.