I love these things, even though I can't purposely watch them and wait to jump off the seat. When I do, I literally SCREAM and throw the headphones right off my head and close my eyes. :p
Who can forget the instant classic "Jingle Bells backwards" prank? I have never been so freaked out in all my life. I totally fell for it the first time. It was NIGHT, and it was DARK in my room. I kept attempting to go through it again but I couldn't. So, I did a print screen/paste in the Paint program and then shrink the picture to get a look at this "monster" face without it giving me a heart attack. ROFL! If you invert the colors in Paint, you'll see what this dude really looks like... and he's a "ginger kid" as Cartman calls the redheads on South Park. :p
I also fell for the one called "Kikia" that has pictures that look like a child drew them or something, then a scary face popped up and screamed. I threw off the headphones in a heartbeat.
I also saw one of the originals, "What Is Wrong With This Picture?"