Warning: Spoilers Off applies to these pages. Proceed at your own risk.
Piccolo's relationship with Pan. He takes a vested interest not only in training her, but also in her home life, admonishing Gohan for being too immersed in his work to spend time with his daughter. He also picks Pan up from school (often enough to be on first-name terms with Pan's teacher). In return, Pan really looks up to Piccolo, treating him like a beloved uncle.
After asking Piccolo to pick Pan up from kindergarten, Videl promises to buy Piccolo a stuffed animal. Despite screaming that he doesn't like stuffed animals, Piccolo has a whole collection of them. Meaning that even if he doesn't like them, he still keeps them because they're presents from Gohan and Videl and that is a relationship he does cherish.
After decades of drifting between various wastelands and Kami's lookout, and fans joking about his homelessness it's revealed that Piccolo finally has a house of his own.
Given what we see of the interior it's implied that the only reason he even built it was to have a place to babysit Pan. For example: it has stairs leading to the second floor rather than just a hole to fly through common in Namekian architecture since Pan can't fly yet.
When a disguised Piccolo makes Pan scream out in (fake) pain to motivate Gohan, Gamma 2 is outraged and demands that he let her go, because heroes don't hurt kids. This is the first step to making Gohan, Piccolo and the Gammas all realize they've been had.
Gohan's Papa Wolf scenes after the Red Ribbon Army kidnaps Pan. Before Mook 15 reveals that fact, Gohan was barely paying attention, not even examining the ki of the strange men who have come to his home. The instant he finds out they have his daughter, Gohan Flash Steps outside and transforms into Super Saiyan, his power carving a crater into the ground so large that half of the mansion falls into it. He's practically snarling as he demands to know what they've done to Pan, and is barely restraining himself on the flight to the RR HQ. Once he sees Pan, he tears his way out of the plane and slams into the ground with enough force to send the Army's mooks flying. The aforementioned moment of Piccolo pretending to threaten Pan is enough for Gohan to stop holding back and go Ultimate, something he usually reserves for situations where the whole world is in danger... which makes a lot of sense, given that Gohan's familyishis world.
In a similar manner, the fact that seeing Piccolo nearly die is the catalyst for Gohan to unlock a more powerful form. Their relationship may have started out rocky, but Gohan really does love his mentor/father-figure.
Gohan gives his mentor arguably the greatest tribute possible; training in secret to learn Piccolo's Special Beam Cannon. Especially meaningful because not only is it Piccolo's signature technique, Gohan would have to invest time training to learn it. Piccolo, who places a large amount of value in taking training seriously, recognizes the effort spent and wholeheartedly says that "it's marvellous".
On Gohan’s desk are two photos: one of him age 4 in his Goku’s arm. The other is a wedding group photo with his father’s arm around him and Piccolo at the back. Gohan cherishes his time with Goku and his mentor.
The reunion between father and daughter as Pan runs up to give Gohan a big hug.
Piccolo acknowledges the Heroic Sacrifice of his Worthy Opponent Gamma 2 to help destroy Cell Max, somberly declaring that "To the end, he was truly a Superhero." To this, the redeemed Doctor Hedo tells the Z-Warriors with a sad smile, "No, may I add, that you are allalso Superheroes." Doubly heartwarming considering that the Z-Warriors present have until-now been relegated to extras sidelined during major conflicts, now finally the stars of their own saga.
During the end-credit scene, Goku seems genuinely happy for Vegeta's "victory". Even smiling after Vegeta claims to have finally defeated him. Even though Goku really only collapsed from exhaustion.
