I don't know if we'll see Aku again considering Mako Iwamatsu died in 2006, though they could go the Avatar route and find someone similar to voice the character like what Nick had to do after his passing for Uncle Iroh.
Space Ghost: Coast to Coast
Aqua Teen Hunger Force [rip]
Venture Bros.
The Eric Andre Show
The Oblongs
Loiter Squad
Rick and Morty
Tim and Eric Awesome Show, Great Job!
Metalocalypse
Black Dynamite
Mike Tyson Mysteries