Boogeyman Zac Skin ! (Nightmare Before Christmas) ish
Originally I wanted this for a new champ, but since that didn't get reciprocated too well. Old: http://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/TJIX16X8-boogeyman
New Idea: Boogeyman Zac (Nightmare Before Christmas) Skin His Passive would be just a giant swarm of bugs trying to get back together.
With every bounce he could leave a tangle of bugs behind. Heck even while he's moving we'd see tiny worms/flies/etc trail behind him.
Then when he does his ult he could unzip that "skin" of his and just bounce around in as a giant swarm of bugs. They could splatter and reform with every bounce.