At the end of "The Last Knight", Michael redeems Fisk and frees him so that he is not obligated to follow him around anymore and starts to leave. After a startled second, Fisk follows, complaining that if he'll only get into more trouble without him.
Anything in Rogue's Home that involves magic from Fisk's point of view. Considering that he's usually so sardonic it's sweet to see him beinng so sensetive to Michael's feelings.
Fisk's Character Development in Scholar's Plot, which is especially rewarding after he hits his breaking point at the end of Thief's War: he finally has a support system again, which he lost in Rogue's Home after his brother-in-law exiles him from his hometown, which was next to impossible to restore because of Jack's betrayal. On top of Michael, whose friendship with Fisk has been restored (and arguably improved), there is the mad jeweler who is the first person after Michael whom Fisk shows great concern for. But the most telling is Kathy, whom Fisk falls in love with. The book ends with Fisk declaring that he'll do whatever it takes to do right by Kathy, making his first conscious effort to stay away from a life of crime since his falling out with Jack Bannister.