In episode 22, the whole scene where Okabe declares his love for Kurisu.
When Okabe sees the D-mail from his future self. Hearing that all the heartache and sacrifice that time travel put them all through is what opened the path to the Stein's Gate timeline. "It all meant something," indeed.
In episode 23, when Okabe meets Kurisu again after thinking he had lost her forever. Doubles as Tear Jerker.
All the lab mems recalling Okabe despite not really remembering who he is. Special mention goes to Mayuri, who says that saying Okarin makes her feel warm inside.
Kurisu finally succeeding in bringing Okabe back to the Steins Gate world line.
From the visual novel, Ruka's ending. Okabe gives up trying to save Mayuri but in order to give Mayuri some happiness before she dies, he sends Ruka back in time a few days so she can cosplay for Mayuri. Doubles as a Tear Jerker.