My first thought was the time I came back to Miami after a week in Peru. I had the worst stomach problems ever. When I got back to the UK I was diagnosed with some bug that lasted for 3 months but the 3 days in Miami were sheer purgatory.
But then I remembered a holiday (?) in Tunisia a few years ago when my wife and I both came down with food poisoning on the first night - what a fun filled week that was. But we weren't the worst as some guests had to be flown back to the UK on air ambulances