Valerie Mayen's Season 8 elimination. Not only very graciously bowed out, but gave different words of support to each remaining contestant, along with why she admired them. The episode was a double whammy of emotion with Mondo revealing he was HIV positive, and the support he got was just as heartwarming. Tim Gunn was teary-eyed watching Valerie go.
Mondo apologizing to Michael C. for acting like a dick towards him during a partner challenge. He had previously said that he thought that Michael C's construction was awful. He came to appreciate Michael C. as the challenge went on, apologized, and the two became great buddies. Granted, Mondo's design made the bottom 3 but mostly it was due to the design and not the execution.
By the end of the season, the friendship between the two had evolved into a true Bromance...which continued during their run on All-Stars.
Daniel Franco in Season 2: although he was making a strong showing, he wound up as the leader of a losing team one week. When the team members were asked which should go home, Daniel stepped forward, accepted responsibility for the team's designs, spoke to the talents of his team members, and tearfully demanded that he be eliminated instead of either of them. Both of his teammates were left bawling their eyes out on the runway. In a situation where contestants often begin looking for someone to place blame on, or even set the situation up in advance to get their competition eliminated, Daniel sacrificed himself for his teammates.
Also from that season, Andrae Gonzalo (and his friendly, outgoing personality) being the glue that kept the boys of room 35D (himself, Santino Rice, Nick Verreos, Daniel Vosovic) together.
After Season 9's Kimberly suffered a series of Disaster Dominoes including sewing through her own finger, she was clearly on the verge of a meltdown. Cue Tim Gunn coming around for his usual critique. He took one look at her and realized she most needed a giant hug, which he promptly gave her. Awwww.
For Season 9's "What Women Want" challenge, the designers had to help male clients design a dress for their significant other. While most of the clients had trouble coming up with ideas, Anthony's client knew exactly what he wanted: a recreation of his wife's favorite dress, which she had lost at an airport years ago. Awww!
Best part was that the husband looked like he was straight out of Sons of Anarchy, but was totally determined to give his wife back her dress. And when she walked the runway, you could tell how thrilled and happy she was.
Season 9's Viktor turning out to have a Hidden Heart of Gold when Tim Gunn visited and met his five-year, Adorkable and adorably enthusiastic and supportive boyfriend.
Season 9 ended with a special 'Behind the Seams' episode hosted by Tim Gunn. It included his presenting awards of his own to designers for things like "Best Time Management" (Viktor), "Has No Comprehension of What Time Management Is" (Oliver), and Best Decoy Collection (Laura.) The episode ended with the designers presenting Tim with a video tribute they'd filmed in which they (except Jerkass Joshua, who managed once again to make it All About Him) told Tim how important his advice and mentorship was to them and how much he'd influenced them. Tim, several designers, and not a few viewers, were reduced to tears.
In the All Stars "Patterning for Piggy" challenge, it was nearly impossible not to smile at many of the contestant's utter Squee over the guest judge Miss Piggy. It was like many of them were having their second childhood.
The smile of the challenge winner Michael Costello is also incredibly sweet.
Likewise, Michael C.'s expression in another All Stars challenge where guest judge Dian von Furstenberg says "Call me" (as in for a job.) The pure joy has to be seen to be believed.
In Season 1 during the postal challenge, Jay's model couldn't come in time for the runway show. So another designer, Austin Scarlett, filled in for her and walked the runway wearing his competitor's design.
Episode 9 of Season 10 has the competitors' friends, family members and loved ones join them to give them inspiration. Much hugging and crying ensued, and even the more Jerkassish competitors gained a few Pet the Dog moments.
Gunner and Chris burying the hatchet during the print challenge in episode 9 of season 10 and bonding over their mutual history of bullying. Considering how antagonistic the two had been to each other made it a very sweet moment, especially when they hug after Gunner is eliminated.
Season 12, Brandon's proposal to his long-time partner after he won Episode 4's challenge. Made even better by the fact it was a week before Prop 8 and DOMA were thrown out by the Supreme Court. Said boyfriend videoed him to tell him... and then he proposed to Brandon!
In the "Glamping" challenge of season 12, Justin winds up on the bottom and gets sent home, and returns to the workroom in tears (soon followed by everyone else) only for Tim Gunn to enter and execute his Save. Even designers who can be more Jerkass were visibly relieved that he got to stay.