TimesOnline: 50 greatest Olympic Moments

I only mention it as I was present watching when this happened:
47. Montreal 1976. Russian fencer Boris Onischenko was disqualified after using a circuit breaker to score points in the epee without touching his opponent. Some suggest he had been using the technology for six years.

As I recall* it was in the Modern Pentathlon, and we were cheering on the British team (I think Nightingale, Fox, and Parker).

It was one of those things where everything stops for an unknown reason while people stand around and talk, then it turns out it was something rather dramatic.

*It's what I remember but it was a long time ago so I might be wrong.