Jack has many of these to counter-balance its consistent horror, although they seem to have died off in the recent years. Still, the strip where Fnar says that he pretends that "Uncle" Jack was his father was incredibly heart-warming. Ironically, Jack really was technically his uncle, although he never knew that. Actually, most scenes with Fnar tend to be heart-warming.
You can't leave out the part where Jack and Farrago finally kiss. Jack accidentally healing Drip's damage and giving her back her wings didn't make it any less heartwarming, either.
And then there's the scene with Jack's true love from when he was alive. It manages to be both heartwarming and darkly ironic, since she clearly doesn't know what happened to her boyfriend...
Pretty much all the arcs involving souls getting closure have this at some point.
"I'll be Hazel and you be Fiver and let me know when things are going wrong."
Any time a damned soul's eyes are opened...provided it isn't a Tear Jerker.
This troper particularly liked one of the scenes in the side arcs:
Vinci: Bash, we've made some bad mistakes. That's why we're down here. But I think you can make a bad mistake turn good, if you learn from it. And, I think there's more good in you than you think. I'll see you later, dear heart.
Bashful: Vinch? This is gonna sound dumb, but I wish you'd've been my dad. If you had, I don't think I would have made it down here.
This troper really liked the short where Farrago despite having her memories of Jack erased, made him a new scythe (to replace the one that had been taken from him) anyway.