I voted for Wotzel & Steuer in the 94 Olympics LP. For those who didn't see it, basically they were skating forwards, Mandy in front, and went into spirals with Ingo holding her hands behind her. She tripped over her toe almost instantly, couldn't break her fall with her hands as Ingo was holding them, and landed hard on her chest and chin. They had to stop the programme and he had to carry her off, and they withdrew.
Another particularly bad fall I saw was by Stefan Lindemann, in some competition in I think the 00-01 season (I'm guessing that, because Plushenko was the next skater and was IIRC wearing his LP costume from that year) - it might have been a GP event or another smaller competition. Lindemann was skating his LP, and went for a triple axel and landed it all wrong - it appeared like his leg, ankle and foot all went in different directions. I don't know if he broke it, but it certainly looked like he did. He immediately collapsed on the ice, and grabbed his leg and was rolling from side to side in agony - the look on his face said it all. Eventually some people in shoes came onto the ice with a stretcher and took him off. That's probably the most pain I've ever seen a skater in after a fall.
Others that haven't been mentioned yet are Elena Berezhnaya in 01 Euros SP, on the throw. She tripped over forwards as soon as her blade touched the ice, landed on her stomach, and slid backwards and crashed into the boards. Ow! To her credit, she managed to get up and finish the programme, but it did look very painful, and probably knocked the wind out of her...