Was living in student housing during an internship one year, 6 guys sharing an apartment, and one night I decide to make sauted portabello mushroom to put on top of my pasta. I add butter to the skillet, and add the mushrooms with a spice mix largely consisting of black pepper and crushed red pepper (hey, I like spicey food), with a couple of other spices to compliment the pasta sauce. The problem, however, was in the fact that putting that much hot pepper into a very hot skillet created a yellowish cloud of pepper gas which managed to gas all of my roommates out of the apartment. I exercised a little stoicism and stood there sneezing and coughing until it was done :P Tasted really good though
My other story is from when I was about 10 and was over at my grandmother's. I went to make something in the oven and just switched it to preheat without looking inside. It turns out that for some reason my grandmother stored pans and the like in the oven. It wouldn't have been a big deal save for the fact that one of them was a plastic bacon tray for cooking bacon in the microwave. Needless to say that was a smokey disgusting mess.