Not as graphic as Oz's story, but his post reminded me of a work (as opposed to school) lunch story I personally witnessed.
I worked in an office with a guy who was kinda strange. He would come in every morning and place his brown bag lunch on his desk, despite their being a refrigerator nearby to store his food. One day around lunchtime a coworker noticed what looked like a small puddle forming on his desk under his lunch. She grabbed some paper towels and was just about to wipe it up as he walked back in. Without saying a word, he sat down, dipped his hand into the lunch bag, and pulled a large piece of meat. In short order he ate it room temperature, then used the papers towels our coworker had retrieved to wipe the grease from his hands. He threw both the paper towels and the badly grease stained paper bag into the trash.