Anytime Frank and Ice interact with each other in a serious manner.
Frank's promise to Merlin and Katya before he dives into the pack of Flankers at Galena and right after both Merlin and Katya declare they're staying with him all the way.
“I...” Was the world always that watery? Shit, you tell yourself. Military bearing. “When we get outta this, Katya, you and me, we'll go down to this park I know about back home. I think you'll like it.” You say. “Merlin, I'm gonna have Santa cook you up a cake bigger than you are.”
Icequest, where Ice, despite suffering from a Heroic BSOD of her own, goes to to help the rest of the girls recover from their own Heroic BSODs after Frank crashed and was declared MIA, with liberal application of hugs.
In quest 41.5, Frank comforting Merlin after her issues about not being a real witch come up again.
John Kazinski's sidequest, where he proposes to Ilyena, with a ring made from his pilots wings.
He manages to top himself for his Christmas present to her, the first since they were married: Tracking down and restoring her wartime Strikers and her rifle.
Pretty much all of Holly MacLeod's adorkable relationship with her maintenance chief, as they move from being acquaintances to friends to almost, but not quite there yet, lovers.
Mack and Georgette are still as in love with each other as the day they were married. Their dance together, in Castle Barin's dining room, moves Katya and Konstantina to tears.