I already told my worst smelling food story upthread (cabbage that had been in the fridge long enough to liquefy, which then set unrefrigerated in tupperware for some time). The second worst food stench I've ever encountered, though, was the time I, not knowing any better, stored potatoes and onions together in a plastic bag. They engage in some kind of mutually-assured-destruction chemical warfare when you store them together. Both potatoes and onions merged into a single sludge, in a remarkably short period of time for root vegetables, and stunk up the entire house. It took me awhile to figure out what on earth was causing the stench, because it had been less than a week since I bought those vegetables and I didn't suspect them of going bad yet!