There are two, hard to say which was the worst.

The first was in 1994, ORD-YYZ on an AA MD81. The pilot had said prior to t/o that there was weather "But we will be giving it a wide berth". What followed was a terrifying 40 minutes of turbulence so bad the fuselage creaked, a few O2 masks droped, bins fell open, and even the FA's looked terrified. Needless to say, many pax were using the bags and a few who SHOULD have used the bags failed to, or ran out...it was a horrible, stinking mess. Luckily it was a short flight and approach into YYZ was smooth. What was funny was that as we deplaned, the waiting pax could see many of us coming off covered in vomit and a few loudly refused to board to their companions. I kept my dinner down..but it was a struggle.

The other was IAD to PHX on WN in 2008. 737 obviously, cannot remember which series. The jet stream was shooting right across the southwest/south, and turbulenceforecast.com was showing a wide swath of "severe" from PHX all the way back to New Orleans. The turb started right on take off and did not stop until wheels down in PHX. It was not quite as hellish as the AA experience, but it was bad enough to get most of the pax ill and cause screaming..and the worst part was that it went on for 3.5 hours....it took that long because of the headwinds so the whole thing was dragged with additional time. Pilot went up as high as 40 and down as low as 25 and it was bad at all levels. It was too wide to get around without a fuel stop. Yes, it stank of vomit in that cacaphony of screaming kids and adults. Not fun.

Incidentally, I am sure some FF's have seen "barf boulevard" at MCI...in the USAirways terminal you can go downstairs and there are some washrooms there. The gates on the lower level are for the commuter props..beechcraft etc. As the weather is usually unstable at MCI if you sit down there and watch the flights come in and the pax deplane, you tend to see people loosing their lunch as they sprint for the washroom, or at least carrying a white baggy or two and the carpet has stains all over it. Kind of sad....but I see this every time I am there which these days is every other month or so.