The fact that Fred was willing to give up Heaven to stay near Stacy is truly an expression of unquestioning love.
The "Other Better Prom" that Deb!Jane throws for Nina and Julia at the end of season 3's 5th episode. Especialy after the entire senior class shows up, and the girls are shown slow-dancing and staring deeply into each other's eyes. What makes it even better is Onerepublic's "All This Time" being played in the background.
Also a Tearjerker, when Elaine, Jane's mother on her death bed, while not fully understanding the reason why, admits to Deb that she knew on some level that she wasn't really her daughter, but that all the same she loves and is truly proud of Jane!Deb right after which Elaine dies with a serene look on her face.
The whole relationship between Jane/Deb and Stacey. Right from day one after Deb becomes Jane, Stacey accepts her unconditionally and is always her biggest supporter. It's an example of unconditional platonic love that this troper found very sweet.