When I was about 9 my family went to the jorvik viking center in York. They had a ride thingy where you could be driven around a realistic viking settlement and whatever the fuck they used to make the realistic smells of smelly vikings and pig shit really fucked me up. No one else was that bothered but I couldn't eat properly for days.
I'm guessing whatever chemical they used really didn't sit well with me. It must have had a pretty extreme effect because that was 31 years ago and it was the first thing that popped in my mind when I saw this question.
Encarta