Episode: Season 9, Episode 1
What happens: Although he is first introduced as a jocular bro, McSteamy's death is probably one of the most painful ones on this show. One of the surgeons in the plane crash, Mark doesn't die immediately in the wreckage, but he suffers from pretty grave injuries because of it. After being in a coma for a month in Seattle, he eventually dies when the hospital turns off life support machines (as he wished for in his will), reuniting with Lexie in Grey's Anatomy heaven at the beginning of season nine.