Renekton
To be one of the most dominant LoL champions during the early game and mid game, it's to be expected that Renekton has no cost to his abilities, making it so that he can fire off abilities off cooldown in lane!
His secondary bar, instead, contains a resource called Fury. Unlike Tryndamere's, which is needed for his Q to work, Renekton's Fury only empowers his basic attacks, and is not needed to cast them at all!
Sett
Much like Renekton, Sett also uses a form of Fury called Grit. Unlike him, however, Sett's Grit is not generated by his own basic attack and basic abilities, but rather by the damage he takes!
With it, he can empower his W, giving himself a giant shield and dealing enormous damage in return. And, seeing as Sett is one of the best juggernauts in LoL, having just one ability dependant on a resource that generates from enemy damage, something that is virtually infinite, he is a prime pick for lane sustain!
Mordekaiser
The secondary bar for Mordekaiser is dubbed Shield, as it shows how much his W will shield and heal him for when used. His other abilities have no mana cost, as he doesn't even have mana as a resource.
This usually comes as a surprise, seeing that Mordekaiser deals magic damage with all of his abilities, as well as the fact that very few champions in League of Legends are truly manaless the way Mordekaiser is.
Kled
Most champions with zero-cost abilities LoL has to offer, actually use a resource that they can stack to empower their auto attacks, attack speed, or use one of their basic abilities, as there are very few champions who truly need no resource to cast anything in their kit!
Kled finds himself in between these two groups, as his only resource is called Courage!
This resource only starts stacking once Kled's mount Skaarl runs away from taking too much damage, returning him to Kled once he has bolstered his bravado with his Courage resource.
All of his other abilities have no cost, and can be used freely as long as they are off cooldown!
Yasuo
As one of the best juke champions in League of Legends, found in the lane that is known for quick bursts of abilities and the careful usage of mana, Yasuo is an oddity in the fact that he is manaless!
Instead, the ability that makes him such a good juke champion is what generates his resource called Flow. Once it generates 100, it automatically gives Yasuo a shield upon taking damage.
None of his abilities, basic abilities or ultimate, depend on resources for casting and can be cast freely!
Yone
Just like his brother, Yone is maneless, with none of his abilities requiring any resource to use, and having zero cost. Furthermore, even the stacking effects are based on stacks and not a secondary bar displayed below the health bar!
Due to this, the only thing that restricts Yone are his cooldowns and the fact that his abilities have a cast time, something that not many other melee champions do.
Riven
Playing Riven effectively takes a lot of practice, as she has a high skill ceiling and is one of the hardest LoL champions to play, in general. After all, executing her combo onto an enemy champion takes multiple animation cancels to pull off.
Luckily, one of League of Legends' game mechanics is not needed on Riven. Namely, resource management, as all of her abilities are zero cost, and are only restricted by her cooldowns!
Compared to most of the other champions, Riven is an old champion whose kit still holds up to the modern standard of League in the right hands!
Garen
There is a simple reason why Garen is not only one of the best top laners for beginners but also one of the best beginner champions in general. And it's the simplicity of his gameplay, that allows beginners to focus on gathering game knowledge instead of pulling off combos!
His kit has no skill shots, with his Q being an empowered attack with a silence debuff, his W granting him a shield, an E to deal AoE damage in a team fight, and a point-and-click ultimate to execute high-value targets with true damage!
All of this adds to the fact that Garen is a completely resource-free champion, with incredible out-of-combat health regeneration and no secondary bar for mana, battle fury, or any resource of any kind!
Bel'Veth
The age difference between the oldest LoL champions and the modern ones is felt keenly with Bel'Veth, due to her kit which allows her to ignore the maximum attack speed possible in League of Legends, in addition to making her one of the best scaling champions in the game due to her infinite scaling!
So, seeing this, it's no wonder that Riot Games also decided to make Bel'Veth a champion whose abilities are all zero-cost abilities, with the only restriction being their cooldown, boosting her effectiveness in the jungle.
Though not as much as the final entry on our list, as she needs some time to ramp up!
Viego
When learning how to play jungle, players must pay close attention to their resource management, and rely on blue buff for the bonus mana to help them along. Viego needs no such thing, denoting his identity as one of the most overloaded LoL champions!
This is because Viego is a manaless champion, with zero cost abilities, needing no resource management, and being free to give his blue buff to his mid lane allies that need it more!
Thus, being able to use his mist to gank enemies, and always have enough resources to execute his combos in skirmishes against the enemy jungler moves the jungle from one of the hardest roles in LoL, to one of the easiest with Viego!