In "Our Man In Toyland," Max and 99 argue about who's going to make a Heroic Sacrifice for the other. They keep jumping in front of each other and pushing the other aside, telling the villain of the episode to shoot them. Max wins. (Fortunately, the "gun" only shot rubber darts.)
In "I'm Only Human," Max resolves to go rescue Fang from KAOS, despite a direct order not to. As he leaves, 99 tells him, "Max, you can't... not without me." After a brief pause, he wordlessly takes her hand, and they head out together.
The gutwrenching opening of "99 Loses CONTROL" where 99 tells Max she's leaving CONTROL to get married. The heartbroken way Max looks at her the entire time, the way he both tries to beg her to stay and hold himself back from revealing too much (to himself as much as her) is just so heartbreaking. It may be Don Adams' most powerful scene ever. You can really feel how crushed Max is and how much he loves her.
"The Impossible Mission": Which is more heartwarming — the Almost Kiss at the beginning...
Max: 99, this is a very dangerous assignment.
99: Every assignment is dangerous.
Max: I don't understand you, 99, you're a girl — why do you want to run around all the time getting shot at? I mean, what kind of life is that for a nice girl? You want to get married someday, settle down, raise a family... After all, 99, you're a very attractive person...
99: Are you trying to tell me something, Max?
Max: Yes... (they lean in, but he, of course, suddenly pulls away at the last second) You can go on the mission.
... or the Love Confession and proposal when Max thinks they're about to die?
Max: You see it's not easy to say...
99: To say "I love you," Max? (he nods) Well, then, why don't you let me say it for you? I love you, Max.
The entire plot of the episode "The Spirit Is Willing": KAOS agent Mondebello assigned his assistant Vogel to kill his secretary Ann Ferris when she uncovered incriminating evidence about him. It turns out she's still alive. Why didn't Vogel kill her? They were in love, and they came up with the scheme involving the sťance to try to get enough money to escape KAOS and run away together. When Mondebello's about to shoot her, Vogel tells him to shoot him instead. He does, and the same girl who earlier rejoiced that he was about to become the first agent to defect from KAOS and live rushes to his side and cries over him. The episode never reveals whether he made it or not...
"Run, Robot, Run" also contains a Love Redeems B-plot. After Mr. Sneed and Mrs. NeilBooby Trap Max's apartment, they pull a Fake-Out Make-Out to avoid getting caught in the hallway. He apologizes to her first, and she says she understands, but it's clear when it's over that they both enjoyed it. At the end of the episode, of course, their plots have all been foiled, but they don't really seem to care, and, since they know KAOS won't forgive this failure, they decide to quit and run away together.