There is difference between scam coin and shit coin. Scam coin promises something and does not deliver (also includes IPO, ICO, Hidden premine scams etc). Shit coin promises nothing and delivers nothing (coin dies due to lack of interest/growth). "Scammiest shitcoin" as you say is new category in my opinion.
There are not to many coins around to fit both categories.
The xCoin come Darkcoin come Dash shit beat then all hands down.
It had more forks than anyone dares to count, the design of the coin promises a spectacular end.
The instamine scam is well known.
Any fool who thinks the aon is of any use is welcome to report of the really nasty stuff done, lol.