Jonah Hex. Easily one of the most memorable historical figures that the Legends encounter and one of their most trusted reoccurring allies. Lots of fans are hoping he can become an official member of the Legends.
Beebo, full stop. This blue furball became beloved by both the fandom and the crew, memeing him left, right and centre. He would became an Ascended Meme of sorts and the crew turned him into a Running Gag that would infect numerous other shows in the Arrowverse. Beebo's influence ended up getting so big he would eventually become a Series Mascot for the Legends.
Season 1
Future Oliver Queen from "Star City 2046", an Old Superhero from a Bad Future. He was a One-Shot Character in easily one of the best received episodes of Season 1. He was even popular enough to return in the COIE crossover 3 years later.
Season 2
The Black Flash, a nearly unstoppable undead speedster that pulls a Big Damn Heroes when Thawne and his time remnants threaten the Legends.
Evil Rip Hunter garnered a lot of fans, with his villainous portrayal being very enjoyable.
Axel, Mick's pet rat, if not for any other reason, then simply because he's Mick's pet who the arsonist cares for dearly.
Season 3
Gary, the Butt-Monkey Time Bureau agent who has his fanboying of the Legends severely tested by having to clean up their crap. He was finally promoted to series-regular in Season 6.
Leo Snart was very warmly received, having all of the humor of his Earth-1 doppelganger but also being a Nice Guy. Helps that, unlike old Snart, he wears his comic basis' costume.
Season 4
Garima was very popular after appearing in Tagumo Attacks, and fans were happy when she appeared in promotional photos for the mid-season finale.
Kitty Zari. Zari being transformed into a cat in "Legends of To-Meow-Meow" which fans fell head over heels in love with.
Puppets of Tomorrow. Also from "Legends of To-Meow-Meow" where Sara, Ray, Nate, and Zari get turned into puppets due to Rory being irresponsible with the Fairy Godmother's power.
