I've performed in a ton of local musicals, so I have some bias towards those as I'm so familiar with the material. Rent, Little Shop of Horrors, and Godspell have been my favorite shows to be a part of, since they all have outstanding chorus parts. Since so many people are in so many scenes, some of my best friends have been made through being a part of those shows and working on them together. I really, really miss being a part of local musicals, and it's something I'm hoping to get back into someday.
As far as seeing them or listening to the soundtracks, Book of Mormon was one of my favorite live experiences of all time, and I also loved seeing Wicked despite not being a huge fan of the score aside from a few songs. I haven't sat down and listened to Hamilton, but I really want to save that experience for when I can afford tickets someday so it can feel as fresh as possible.
Les Mis is great, The 25th Annual Putnam County Spelling Bee was hilarious live (and has some excellent songs), and I also loved seeing Reefer Madness: The Musical when a college near me put it on.