Baseball
It wouldn't be America's pastime if it wasn't inherently dangerous. Baseball is riddled with regular injuries that can be caused by long term repetitive motion or blunt force trauma. Baseballs are hard and they travel extremely fast when they come off of a bat. If you get hit, you're probably going to have a bad time.
It's Up There
While baseball is by far not the most dangerous sport out there, people get hurt quite often. Despite this, has been one singular death attributed to baseball over the course of its existence. A player was struck with a pitch and he died instantly. Just know that you're much more likely to get badly injured than killed, for the record.