So far, I've done Sunrise, Twilight, Eternity, Kudzu, Bifrost, Nevermore, Aurora and Vision for legendaries. I've got enough mats for a couple more, so I'm trying to choose what to do next.
Although it can be very frustrating (looking at you Vision), the collections and crafting is what I find the most fun. I only regularly use about 4 of my legendaries. The rest were just for fun. I especially liked how Kudzu would afford you locations to garden Primordial Orchids and similar bonuses with other legendaries.
What legendaries have you had the most fun with collections, crafting, and rewards besides the final weapon itself?