1. Quaid and Melchio as all Elemental Attackers
2. Elimo and Aurelia as a harmony DEF Booster
3. Sargavel, Lario, Claire, Ruby, and Miku as Spark Team
4. Vanberk and Eric as one of my first and seconds rare summon.
Well I'll break the mould and state some personal reason why Yuura is my favourite.
Apart from his usefulness as a unit, I love his lore and design. Starting with the latter, he looks like an archetypical necromancer but with tiny quirks. The way he stands just SCREAMS COME AT ME. No fear, no remorse. He looks like he could toy around with you while knitting a sweater with your entrails and giving it to you as a joke.
His lore really hammers in the fact that he is an uber badass but with a nice side as things go by, even willing to die many times over until nothing is left just so his friends can deal some good damage
feeva and nadore are my favorite units, first because both of them are ridiculously useful in almost every situation and second, becuz i see them like my summoner´s bodyguards XDD no one is messing with me when those two are around.