Werner Theodor Otto Forssmann, a German surgical trainee in 1929, is famous for an experiment he performed on himself.
Without any direction, he put himself under local anesthesia, incised a hole in his arm and pushed a catheter all the way up his limb and shoved it into his heart. He performed the procedure with two feet of cable, after which he walked to the X-ray room.
He was fired after this stunt but was awarded the 1956 Nobel Prize for Medicine for developing a procedure that allowed for cardiac catheterization.