Wesley Dodds A.K.A. the '30s Sandman coming out of retirement in Starman #22. The splash panel of the last page where he decides to put on the costume one last time and rescue Jack, even if it kills him (he's in his 80s) certainly qualifies.
Solomon Grundy's gentle incarnation, or Solly, had a chain of completely awesome moments: the Infernal Doctor Pip, an insane arsonist, was demolishing building after building in Opal. So Jack goes to stop him; in the process, Pip escapes, and Jack is trapped in a crumbling building as it collapses. Just when he thinks he won't make it, the debris stops... and it's Solly, repaying Jack's kindness by holding the debris for long enough for Jack to escape. He then falls himself, crushed under the weight. With the help of the Floronic Man, Batman, Green Lantern and Jack go into a Battle in the Center of the Mind into Solly's mind to do battle with the other, evil Solomons... and begin losing. Then the aged Starman, Ted Knight, goes into the same battle... and turns up in full Starman regalia, in his prime. He then begins brawling with them, turning the tide, scaring the other Solomons enough to let the others leave... though Solly still dies, completing his Heroic Sacrifice.
The Infernal Doctor Pip, maimed and nearly killed in the blast that killed Solly, prepares to destroy a crowded building as his swansong. Just as Green Lantern, Starman and the regular police fail to stop him in the wake of losing their powers on an unrelated event, the Shade appears, and uses his shadow powers to dump the Infernal Doctor Pip in eternal darkness.
On one corner: Doctor Phosphorus, an irradiated, nigh-indestructible monster with flame powers capable of melting steel with his bare hands. On the other: elderly scientist Ted Knight. Phosphorus is utterly owned by the frail, aged nerd. Twice.
The entire Grand Guignol arc. The Shade's worst archenemy, Simon Culp, has stolen his shadow powers and encased Opal City in an indestructible bubble of shadow, primed to swallow the entire city into a shadow void, after being looted by an army of supervillains. One by one, all of Opal's defenders are captured to stage a mass hero execution. And then, one by one, the thread unravels: first, the heroes escape; then, they begin eliminating the villains, from crushing Doctor Phosphorus to death with a slab of pavement, to tricking an Ax-Crazy convict to teleport himself, smashing himself to atoms in the process, to duping Culp into absorbing the Shade's last loyal shadow imp and losing everything, including his own shadow powers, in the deal, to shattering the curse holding the bubble into place, and releasing an allied army all over the city to counter the few supervillains left... and then a hidden nuke comes into play. There's no time to find it, no way of escaping. Theodore Knight, Starman, uses his last invention to rip the entire building from its foundations and take it into orbit to safely detonate, making peace with his enemy and pulling a last Heroic Sacrifice.
The last Talking to David issue. Jack, his brother and father gather for a last, final time to review the Starman legacy. Also very much a Tear Jerker.
The arc where Jack is sent to the past has him convincing his father, without telling him who he is, to return to help them against family archenemy the Mist. Ted does help them foil the Mist's plan... and then realizes they won't be in time to help stop the villain. So he takes back his costume and power rod, and returns to beat the Mist and his Soviet allies to a pulp. When he's bound to go, Jack convinces him to go to a party to help relax. Hours later, he tells his brother, who reminds him of something that happened in that party... Ted met his future wife and mother of his two children.
The series' finale. Lone supervillain the Spider attempts a last time to kill Jack through a high-rise window. Beat cop Mason O'Dare shoves him out of the way and takes the arrow to the heart himself. Everybody shrieks in horror and rage, and the clouds grow dark from above. Lightning strikes... and Mason is good as new. Zatara's final magic trick, pulled as a wedding gift to his apprentice, Mason's fiance.
The Blackest Night issue. Black Lantern Starman rips out Shade's heart out, and the darkness begins pulling him... and he denies the call. He ruins the black ring and channels his powers through the heart the Black Lantern was still holding. Said Black Lantern is thrown into limbo after being wrapped in the heart's tentacles. And Opal is still saved.
Jack making a stand, however short-lived, against Captain Marvel. And how Opal's citizens shame Marvel into realizing what he's doing is most definitely not the right thing.
The Shade, a Anti-Hero / Anti-Villain (depends on the story) who just happens to be an immortal English gentleman who controls darkness, once got contacted by a powerful demon called Neron who offered him to increase his powers in exchange for his soul (the whole thing being a prologue to an important Starman story). The Shade declines his offer with such style that it was even more satisfying than watching him beat the crap out of Neron.
Neron: You will rue the day you declined my offer! The Shade: Rue? If I had a rue for every time someone said that, I'd own Paris.
Mikaal's eulogy for Ted Knight's funeral at the end of "Grand Guignol".. This trouper still cheers.
Starman, throughout the movie, tries to learn human customs and sayings, and when to use them. At a gas station, he gives a trucker a thumbs up in the men's room and tells him to "take it easy," having learned the gesture from the station attendant. The trucker flips Starman off and says, "Up yours." Later in the movie, at the diner where Starman runs afoul of a group of hunters, Jenny chases them off with her pistol,helps him into her car, and fools the hunters into thinking she means to run them down. One of them yells out, "Take it easy!" Starman doesn't miss a beat and flips him off, "Up yours," as Jenny drives off.