People who sneeze / cough without covering themselves or moving away from the food when getting food from a buffet. I've seen that happen about a dozen times at my local Chinese buffet and it makes me think they're white trash everytime. And it makes me not want to eat the food they coughed over for the rest of the time I'm there, even though it probably happened to other areas.
TL;DR: Buffet food is disgusting.