The launch cable on the Intamin Accelerator Coaster snapped inuring a father and son in the front seats. Source
Accidents
Theme parks and roller coasters are statistically very, very, very safe. Out of the millions of people who ride the thousands of rides every year, there are only a small handful of incidents. You are statistically more likely to be involved in an accident driving to an amusement park than having one at a park. The rarity of accidents is one reason why the media report them, similar to plane crashes.
Every important element of a ride is inspected on a regular basis and every ride is tested every day without passengers before it opens. A ride might not open, or a safety system might activate, if there is an imperfection. For theme parks to operate, they must obtain insurance and one stipulation is their rides are frequently inspected and signed off by a strict Health & Safety governing body. Every theme park does what they can to prevent accidents because the negative press would be bad for business.
Having said all that, theme park accidents still happen…
Big Dipper, Pleasure Beach Blackpool, UK
Two of the classic wooden coaster’s trains collided inuring 21 people. Source
Formule 1, Parc Saint Paul, France
A 35-year-old woman died of a heart attack after being ejected from one of the Pax Company coaster’s cars and falling 16 feet (5m) to the ground. Source (in French)
Firehawk, Kings Island, Ohio, USA
A man died from an undiagnosed medical condition after riding the Vekoma Flying Dutchman coaster. Source
Monorail, Walt Disney World, Florida, USA
Two trains collided head-on killing one of the drivers and injuring several others. Source
Dueling Dragons, Islands of Adventure, Florida, USA
A male worker suffered head injuries when he walked under the overhead track and was hit by an oncoming train. The incident took place during early morning testing, so no riders were onboard the B&M inverted coaster. Source
Bahari River, Holiday World, Indiana, USA
A filter pump malfunction on the lazy river water ride caused fumes that sent 42 people to a hospital with breathing troubles. Source
Go Gator, Ducketts Common Funfair, North London, UK
A 2-year-old was killed when he walked on to the track and was hit by the kiddie coaster. Source
Tomahawk, PortAventura, Salou, Spain
DJ Jump, Travelling Funfair, UK
An 11-year-old girl was throw from the ride after the restraint opened, suffering a large head wound. The seat belt that could have prevented the incident was so poorly maintained as to be unusable. (Source link no longer valid)