Book of the Still: "Iíve been engineered to love you, Carmodi. With the Doctor... itís the real thing."
The scene in Unnatural History where Dark!Sam kisses Fitz for "taking care of her" when the Wild Hunt changed her into a wasted drug addict suffering from terrible withdrawal and Fitz promised to stay with her anyway.
Straddles the fence between Heartwarming and Tearjerker, but the scene at the end of Earthworld when the Doctor finds Anji in the butterfly room and holds her while she cries. It's actually quite bittersweet for both of them, as the Doctor finally has his TARDIS back after one hundred years spent Walking the Earth, but hasn't recovered from his Laser-Guided Amnesia and doesn't recognize what was once a place of deep emotion impact for him. Meanwhile, Anji has just lost her boyfriend of four years and is finally coming to accept that he's gone. The kicker for this troper?
"It was then that she noticed the chrysalises. They were everywhere. By each daisy, on each twig. There must be thousands of them.
"What are these?" she asked the Doctor, without turning around. "What will they become?" "I don't know," he said softly. "But it's new life. Isn't it wonderful?"
Despite the fact it only really has one scene in which they actually interact, everything in Parallel 59 about the relationship between the Doctor and Fitz is very sweet. The last line is especially touching. There are some possible rather bittersweet I Want My Beloved to Be Happy implications if you interpret the relationship between the Doctor and Fitz that way, since the Doctor is seeing Fitz's tearful reunion with the Girl of the Week. But aside from that, since it comes after the Doctor was separated from Fitz for a week (which, considering how the Doctor carries on, seems to have felt much longer), although he's mainly just thinking about the aforementioned tearful reunion, implies rather strongly that in some sense, the Doctor loves Fitz:
He whistled as he walked, Fitzís plaintive little melody still in his head. Thinking of loved ones, coming home.