In an interview with QTV, Alex Trebek recalled an instance where a contestant on Jeopardy! held a meeting with her friends and family to see her on the show, but the episode was replaced by a local program. Alex commented that it didn't matter to the contestant that she miserably wound up in third place, but she wanted to see that event that was significant to her. When the contestant complained, Alex apologized (despite having no control over the happening) and sent her a video tape of the episode so that she and her friends could watch it instead of the contestant losing that spotlight as the next episodes went on.
This is now SOP for Jeopardy!; if a contestant's local market has preempted the episode, a copy of the episode can be requested for free. (If the contestant wants a copy of an episode that did air, it's over $100.)
About a month after Hurricane Katrina hit in 2005, New Orleans native Deborah Slattery happened to be a contestant. Each of her three games was prefaced by an announcement from Alex that Deborah and her family were safe.
March 27, 2013: Challenger Tom Carroll appears on the show, having tried out for 37 years before being selected. And he wins $32,000.
December 5, 2013: Before the Double Jeopardy! round, Alex points out a man who proposed to his fiancée in the audience. She said yes.
Arthur Chu (2014). While many fans have expressed ire about his gameplay, Chu has done a couple of genuinely heartwarming things, which would arguably make him an Anti-Hero.