Here's an interesting video clip of the world's largest production helicopter, the Mil Mi-26, being wheeled out of a hangar in Belarus and taking off. Note the size of the human figures for scale - this thing's huge! It's rated to carry 20 tons of cargo, about the same as a Lockheed C-130 Hercules transport. Officially it can carry up to 90 troops, but in practice it frequently carries more passengers. (For example, in 2002 one was shot down in Chechnya, killing 127 out of at least 140 people on board.)
This particular aircraft was apparently painted in its camouflage pattern for use in the film 'A Good Day to Die Hard', the fifth episode in the 'Die Hard' movie franchise.
Impressive beast, isn't it? Amazingly, Mil built a much larger helicopter, the V-12, in the 1960's. However, only two prototypes were made, and it never entered production. This leaves the Mi-26 and its predecessor, the Mi-6, as the largest production helicopters ever to enter service.