Another vote here for Fantastical. I don't think I'm using it in any novel ways, or really pushing it's power, but wow is it a nice calendar. My only gripe, and probably something I can change in a setting, is sometimes when I have a drought of events, it can be confusing what's next, because it will show me something a month or so out but not in a clear way that the event it is showing me isn't tomorrow. Probably a "me" problem, but one of my few gripes about the app - the other being a desire for better Watch complications.