Heartwarming: Luigi's Mansion

  • The ending of the game, when Luigi has finally gotten Mario's painting back after a horrifying night. The Prof. decides to use his machine in reverse, sending Mario through a ridiculous course with much comedic hollering. What makes this a heartwarming moment, however, is Luigi's reaction when Mario bursts out the other end of the machine, fully alive, but with a grate stuck over his head. Luigi opens his mouth in a wide smile, like he can't believe it, cries just a little bit, and lets loose a most heavily relieved laugh. It Makes Sense in Context, and when you've gone through the events Luigi has, overcoming his fear for his brother... That one moment makes it all worthwhile.
    Luigi: Mario.
  • Visual Gag. The ballroom dancer ghosts have the same heart. They share a heart!
  • Cheering up the various crying Toads throughout the mansion. The uplifting little jingle that plays when they turn the lights on for you helps as well.
    Toad: Thanks, Luigi! You made my dark and stormy night!
  • King Boo of all people gets one. When speaking to Luigi right before his fight, he calls his fellow Boos his "friends". Not minions. Not allies. Friends.
  • Madame Clairvoya's final conversation with Luigi. Amidst a mansion that is filled with Portrait ghosts who are all either vain, self-centered, greedy, or some combination thereof, she's the only one who is nice to Luigi at all and even helps him try to find Mario. She even even volunteers herself to be caught for Luigi as opposed to living an eternal repetitive half-life, unlike the others who are happy to do the same basic activity they did in life over and over again.