Heartwarming / Warhammer 40,000: Space Marine

• The message from Nathaniel, one of the people on Graia, saying that no matter how hopeless things may be, he will look for his son.
• The Blood Ravens arriving to help out is pretty heartwarming when you realize that they weren't given any orders to come. They just happened to be passing by and decided to Screw the Rules, I'm Doing What's Right! and come down to help out their brother-in-arms.
• The first time Titus and his comrades encounter the remaining Imperial Guard on the planet. A small force of troopers is struggling to hold back yet another massive wave of orks when the Space Marines arrive to help. After the battle is done, the surviving Guardsmen reverently kneel before the Space Marines, thanking them profusely for saving their lives. Captain Titus just smiles.
  Titus: Rise, Guardsmen. You saved yourselves.
• As the main characters pass through a triage hospital a badly wounded, likely dying Guardsman says "At least I lived to see a Space Marine."
• Lieutenant Mira starts to chastise herself and her men for not being able to retake the gun battery.
  Titus: You survived this long on your own Lieutenant -- you have done well. But you are no longer alone.