2. Gladiator
Ridley Scott encountered an unexpected problem when Oliver Reed died of a heart attack during production of Gladiator in 1999; though it wasn't as drastic a blow as, say, the prospect of Russell Crowe dropping dead on set, it still created a massive issue given Proximo's importance to the plot, and the fact that many key scenes and shots had yet to be filmed. While CGI was used rampantly by this time, it still proved to be one of the most ambitious and daring manoeuvers in major blockbuster filmmaking at the time; the production forked out over $3m for a visual effects company to create 2 minutes of new footage, in which a double's face had a digital version of Reed's face mapped onto it. What's most incredible is the seamlessness of this job; it's subtly cosseted into the film and doesn't detract from it at all. We've all seen that terrible Sopranos episode where Tony's mother, Livia, has a super-imposed CGI face mask, though with TV budgets being more restricted, the hatchet job wasn't able to convince, but here, there's never really any doubt that it isn't Reed we are seeing. Incredible.