one on the x-acto knife, in this case a large box cutter. My school was a short block away from a hospital, and one morning, close to the end of first year studio, we walk in to the main hallway to find a trail of big blood drops going out and in the direction of the hospital. One of my classmates had been working on his model and using the box cutter on a table with the blade towards him, and sure enough, one of his passes went too far and landed on his thigh, opening a 6" gash. He walked to the hospital e.r. and had it stitched, bu the blood trail stayed for a couple of months for everyone to see.
Lots of sneaking onto the roof of the building to watch the sun rise over the Santa Catalina mountains...