Can you think of any others? I know of just one - Dallas, which ended with the devil convincing J.R. to shoot himself. Seriously. Later ret-conned in a post-series movie.
Of course Lost hid Jack's suicide well. It even portrayed it as a heroic sacrifice. But it was sadder than that.
"You're committing suicide!" said audience surrogate Hurley. And Jack had no valid response. If Jack wanted to live he could have easily. Sent Desmond up, got the rope back, only then stuck the cork back in and then rode the rope the safety before the light returned. But no. He killed himself.
He'd been suicidal for a long time. Off the island, he'd been boarding planes every weekend. Hoping to crash on the island, or simply to crash. Suicidal.
Then, the culmination of this slump, Jack stands on a bridge and prepares to jump. Suicidal.
He returns to the island. Initially, he lacks purpose. Then, heavy with regret, he tries to erase the last years of his life. What do we call most people we try that? Suicidal.
Flash forward to 2007. Dogen tells Jack to feed Sayid a pill. If Jack thought the pill medicine, he'd have given it to Sayid. Certainly swallowing it himself wouldn't test its efficacy. Instead, Jack mistrusts Dogen. He swallows the pill himself. Suicidal.
thumb|400px|rightNot too long afterward, Richard asks Jack to light a fuse. Jack does... and watches it burn down. Completely irrational. Not rational in a "man of science" way, but not even rational in a "I can walk, therefore this island is special" way. Even with all the knowledge we've since gained about the candidates, Jack lighting a fuse to kill Richard should have killed them both. Jack was willing to risk it. Suicidal.
Then comes Jack's final act. He could have saved Desmond and himself. No ticking time bomb prevented this - The Heart had been uncorked for hours; another minute wouldn't have hurt. Jack had to die. Suicidal.
And proving that I'm not just making all this up, we get to hear Jack's reasoning for his sacrifice. For the "greater good"? Because "it's the only way to keep them safe"? Because he "said he'd get them off the island"? No. Jack says, baffling Kate, it's because "the island's all I’ve got left. It's the only thing in my life I haven't managed to ruin." Suicidal.
Of course Jack stands on the shoulders of suicidal giants. Juliet's the example of the death some call a sacrifice but was most obviously suicide. She'd fallen thousands of feet and rightly chose to end her life / possibly reset time rather than slowly bleed to death. Suicidal. We've mercilessly analyzed Charlie's death, and we've concluded he didn't swim out the window / close the door behind him because he chose to "accept his death". Suicidal. Locke tried hanging himself to save his friends when he could have tried any number of more effective methods. Suicidal. Michael went on the Kahana to save his friends but also "to die," having previously tried killing himself without saving anyone. Suicidal. Jin stayed with Sun knowing he'd die and even though he couldn't save her. Suicidal.
(Those are just the allegedly heroic deaths. Numerous other people have committed suicide as well.)
Of the all sacrifices, only Sayid's (which alluded to suicide bombers) and Desmond's (which didn't even kill him, either time) saved people without needlessly killing a suicidal hero.