Surstromming is a pickled fish in brine, sealed in containers and allowed to ferment. The process takes about six months. The resulting fermentation causes the tins to bulge, thus quite a bit of gas will escape once the cans are punctured, and it is believed to be one of the foulest-smelling things you will ever encounter with food. Supposedly so bad that there are rumored instances where firemen or other personnel have been called to residences on concern of a possible gas leak or a broken sewer line, only to learn that someone had simply opened a tin of surstromming. It is considered a culinary dish in Sweden.
http://en.wikipedia.org/wiki/Surstr%C3%B6mming
And here's a nice picture for ya:
And an even better one:
Look on the bright side though....if you can't eat it, you could probably utilized them as stink bombs against those pesky marauder forces....