This would be fun to discuss.
More often than not people find pitybreakers to be a nuisance, either because you already have that unit, they have bad IVs or simply aren't as great as you would expect (looking at you, 5* -Atk Dagger Jakob). But sometimes the exact opposite happens. The last time this happened to me was in the current Wings of Fate banner. While trying for Shigure, a perfect IV Hardin appeared before me. I was like "Hi ! Would you like a cup of fine tea ? (ノ◕Д◕)ノ".
I think the best you can hope for in this game after that one focus unit you want badly, is a happy pitybreaker you didn't know you wanted. What was the most pleasing surprise you had appearing out of nowhere ?
(Jakob was just salty because I sent my first 4* of him home without thinking twice. Ha. :v)