The worst conference presentation I ever made has recently been posted on YouTube by someone called nsicu ru; I probably consented to recording, but did not know it had been so publicly posted.
I was the second speaker in a two-presentation morning session, and the first speaker who disapproves of steady state Starling physiology had filibustered me with his talk, leaving me zero minutes in which to make a 20 minutes presentation. He then insisted I at least start my presentation, you can hear my discomfort at the prospect. During Slide 9 he interrupts me to disparage my message, and we exchange words. During Slide 10 I am evidently shaken and struggling to get the words right; at this point the conference organiser burst through the doors, ran up to me and told me to stop. You can hear the doors opening, but the recording ends before the organiser tells me to get off.