Anything really xD I was reading through another somewhat gruesome manga and then I reflected on all the other horrors that I have read. I then was like must chat with some! But who? PJV!
Hmm, I might try to find it. I've read a medical horror called Emerging which is about a new virus which has some similar properties as Ebola.
As for horror. I've read Uzumaki, Gyo, Deadman Wonderland, Franken Fran, and maybe a few more that I can not recall.
Uzumaki, Gyo, and Franken Fran were all very good with metamorphosis. I also liked Franken Fran's irony. As for Deadman Wonderland. The concept was very interesting and I look forward to more chapters $-$