9. The Visible Gas Canister - Gladiator
There's nothing that breaks audience immersion quite like a piece of modern technology showing up in a period movie, and despite winning five Oscars including Best Picture, Ridley Scott's Gladiator is guilty of an epically unforgettable gaffe.
During the film's Battle of Carthage sequence, one of the chariots gets flipped over and slides along the floor.
As the dust begins to clear, a metal gas canister can be blatantly seen on the back of the carriage, and given that Gladiator is set in 180 AD, it's a device which wouldn't actually be invented for, say, only about 1500 more years.
Unfortunately for Scott, the film's re-releases on Blu-ray and 4K UHD only make the mistake that much more noticeable - and hilarious.