Esophageal blockage
I (Woozle) have a benign esophageal stricture -- probably Schatzki's ring -- which causes certain types of food to get stuck if I don't chew it enough. Normally I can clear these obstructions within a few minutes by drinking water and then (what I shall delicately refer to as) expelling it, but twice now that has failed.
The first time, I ended up at the emergency room, and had the obstruction endoscopically removed. The operation itself was quite pleasant; the long, long wait (since the problem wasn't immediately life-threatening and I wasn't in tremendous pain -- just discomfort) much less so, and the almost-$8000 bill was completely not pleasant at all (although they did later mark it down to $2000, for reasons that remain unclear to me).
The second time -- which I am just recovering from as I type this -- I was able to expel it after about 24 hours using a combination of techniques, ultimately culminating in a bold swallow of slightly-flat Pepsi Cola. (I mention the flatness only to indicate that full carbonation was not necessary).
Apparently there is good scientific evidence that this is actually reliable -- see this study from 1993.
I'm primarily setting up this page as a repository of the useful information I came across while trying to find more information.