I had a similar experience with a friend who decided to cut some electrical tape with a big knife straight toward his hand. I warned him not to do it (like I warn my wife, every time she cuts a bagel), but he shrugged it off. He sliced straight through the webbing between his thumb and forefinger, did a little quick "oh sh*t" face and ran to the bathroom to get something to staunch the bleeding. Then he passed out into the bathtub and had to be taken to the emergency room.
You blew my mind about the bagel as I was just going to type...
When I saw the Weedeater and Serpent Throne show the bassist in Serpent Throne had his middle finger all wrapped up. One of his band members said excuse this dipshite, he decided to stab himself this morning slicing a bagel LOL.