Mansell allowed his Williams to die whilst leading and waving to the crowd...Canada 91. What made it even funnier is that it let Piquet through for his last F1 win. And Mansell disliked Piquet following their time together at Williams...
Interesting that the third car in that scrap was Herbert, who retired from the 1998 Italian Grand Prix after a Sauber mechanic left a pait of pliers in the cockpit of the car. They got tangled under his brake pedal causing him to spin out.
(Wikipedia reports that it was a spanner, but I remember the commentary at the time reporting it was pliers and there was a cartoon at the time which refers to 'a spanner, or rather pliers, in the works'.)
Chinese GP 2005, Montoya retired because he broke his wheel on a manhole cover... That was kind of special... Not a technical failure of the car, but a technical failure of the manhole cover. Those things are usually quite reliable are they not?
Muulka -> That was indeed Webber, Suzuka 2004. 2nd degree burns to the bottom. Shows how long the poor guy toughed it out before he had to retire. I think that has to be in the top 3 somewhere.
Olivier Panis, Silverstone 2004: had to retire because of an exploding... extinguisher. Yes. His extinguisher exploded. That has to be up there among the most ironic technical retirements!