Fate/Zero/Heartwarming

• Knowing full well all the shit ahead of them, the scene of Kiritsugu playing with Ilya while Iri watches on is absolutely heart wrenchingly bitter-sweet.
• Alexander's bromance transcends time, space, and creed.

Waver: “I don’t have Command Seals anymore! I don’t want to be a Master anymore! Why do you still want to take me with you? I—“
Alexander: “Whether you are or are not a Master, you are my friend, and that will never change.”

• • And later

Gilgamesh: "Boy, are you Rider's master?"
Waver: No. I'm - his servant."

• Take a look at Lord Melloi II. Waver is wearing Alexander's colors.
  • That's nothing. Take a look at one of the soldiers shown in Ionian Hetoriri. Look familiar? Loyalty that surpasses time and space indeed.
    • Or it's Eumenes, a general of Alexander whose Indo-European people wore their hair long.
    • With a necktie?
• Every moment with Kariya and Sakura, and then you remember whats going to happen.
• Saber takes Iri for a walk in the city after the latter spent her entire life in a castle.
• In the anime, that there's a whole episode dedicated to Rin is a CMOH in itself. The way she defends her friend Kotone from the bullies and then rescues her from Ryuunosuke is another.
• The scenes used during the 2nd ED, showcasing the development of Irisviel and Kiritsugu's relationship status going from "Magus Killer and Homunculus" to "Loving Husband and Wife" definitely counts as one.
• Waver using all his command spells to release Rider from his servitude. Rider refuses to leave and Waver breaks down in tears.

Rider: Even if you are not my master, you are still my friend.

• In episode 22 of the anime, Waver's conversation at dawn (after having spent the entire night walking back into Fuyuki City after Saber destroyed the Gordius Wheel) with Glen Mackenzie on the roof of their house where Glen reveals he's aware Waver isn't really their grandson, but he's made the elderly couple so happy (they don't see their real grandkids anymore) that Glen asks him to stick around.