Sejuani - I've mained her consistently from the time I hit summoner level 20ish and nothing will ever compare to her in my eyes. She's tanky, full of cc, and rides a huge boar and wields a flail. Not much else to say.
Skarner - Picked him up around the time I hit 30 and I love running ghost, shurelyias, boots of mobility and hardcore punishing bad positioning. He has an amazing laugh and he's a deceptively good duelist/counterjungler even when built straight tanky. Iceborn is evil on him as well.
Fiora - A lot of people rage at me when I run Fiora in the jungle, but it's incredibly fun albeit it's very feast/famine. Camping weak lanes and steamrolling off kills and assists is a lot of fun, and when she gets ahead, she stays ahead (also, I love Headmistress Fiora and hitting things with a meter stick all game)