Well in all my travels, fortunately I haven't had many misfortunes. Probably the most notorious one was back in 2001 in Dubai.
That was weeks after 9/11. Travel and Internet were still far relatives (no online check-in, online information, etc). We arrived at around 6am for a 9am departure back to London after a fewd days holiday in dubai.
For our bitter annoyance, we discovered that the flight had been cancelled. Basically, because the incoming flight never left London. It was the days of great paranoia following those terrorist attacks in New York and travel had been thrown on its head; flight cancellations, delays, increased security, etc.
Unfortunately, they were unable to reprotect us on any other flight/carrier.
Of course, one didn't have the resources or savvy we have nowadays. When we complained that we hadn't been advised, the airlien rep simply told us 'We published it on the Dubai something or the other Times'...as if we would be buying newspapers while on holiday... The next flight was not until 02.30 am next day; lovely 15 hour wait at 40 C! But that was probably the worst mishap i've ever had.