Free Solo Climbing
Although the movie Free Solo should have dissuaded its audience from wanting to try to climb any huge structure without ropes, there has been a boom of free soloing since then. A few dozen climbers die annually from attempting to free solo different climbs, That does not include the hundreds that irreversibly injured because of failed attempts.
Wingsuit Flying
Wingsuit flying (or squirrel suit flying) is similar to BASE jumping (meaning that you can combine the two) is an insanely deadly thing to do. You literally have to trust your body tension with your entire life. If you fail while on a wingsuit, that's probably the end for you. There is no room for an additional parachute, and some of the time, wingsuiters don't even deploy their parachutes.