Well, most of us want him to be an Ego in the Septic Squad
But it is Shawn Flynn from Chapter 3 of BATIM, who is, you guessed it, VOICED BY JACKSEPTICEYE HIMSELF!
Kiyoshilia in Instagram posted this a while ago:

I f***ing live this art Kiyo!
Who else agrees that Shawn Flynn should be an ego in the Septic Squad?

My Instagram: littleannasmith
My mom knows about my account and she isn't mad at me..
Also, Thea was live but I decided to not watch it
It was too dark
And it kept pausing