Our cat, Fysh, sometimes has these episodes where she looks like she's choking on something, and sounds like she's half sneezing half coughing up a fur ball. She's done it ever since Mary got her 8 years ago.
Well, we recently took her to the vet because she has had some trouble breathing (turns out she has asthma). And the vet got to witness the hacking/sneezing fit.
She called it a reverse sneeze (check out the link, it's got a kickin' tune). Evidentially dogs often get it, and it's a pretty accurate description of what happens.
At least we know what to call it now. There's no known cause/cure.