Nanobot Zac / Scrap Heap Zac
Nostalgia: Anyone remember that game?
Disclaimer: This will probably be a difficult read; I'm not much of a writer, so just bear with me.
Anyway, the idea is to have a skin for Zac that's not simply a recolor or a different kind of liquid. I've got two similar ideas here, but there's one key point: both of them retain the idea that Zac can change his size and shape. This is why so many Zac skins ideas are just ordinary liquids, because it's difficult to come up with a good way to retain his amorphous nature using any other type of material.
#Nanobot Zac He would be made up of a central "AI Core", if you will, with the rest of his body being composed of tiny robots, linking together with each other to form his main body. Beyond that, most of his animations could remain exactly the same as now, with some small changes beyond altering particles to fit.
But in all honesty, I would greatly prefer this one instead... #Scrap Heap Zac (tentative name) The closest parallel I can come up with for this is the PS4 character Knack: http://30plusgamer.com/wp-content/uploads/2014/04/Knack_2.jpg If done right, this skin has the potential to be a Legendary tier skin, possibly even Ultimate.
Start off with a kind of electrical Hextech core, surrounded by lots of random chunks of metal (rather than identical nanobots). He would look a bit haphazard and rugged at first. Damaging Zac would cause him to shrink, and lose some of his component pieces, making him look more and more ragged until he finally dies. Conversely, gaining more health would increase his size, pulling new shards of metal from the ground nearby and incorporating them into his body.
The main idea, though, what could possibly make him an Ultimate tier skin, is that as he gains more and more health (every ~1000-1500 health or so, maybe) his basic form changes, becoming more and more tank-like. Gaining more health makes him visibly more durable by gaining larger and broader pieces of metal, gradually building himself into a kind of plate-armored behemoth.
As he is damaged from his fully armored state, he reverts forms, losing pieces of his body until he is finally knocked into his passive. When this happens, several piles of metal shards are flung out from his body, leaving his Hextech Core exposed. The core begins magnetically attracting the metals back to his body, unless of course they are destroyed before they reach him.
I can't really think of a way to describe it in any more detail than that; you'll just have to use your imagination.
