P. gibbiceps. In particular, the variant that has very strong contrast between the lines on the body and the dark shapes formed between them. I have only seen these variants (ok, it may not be a true variant; it could just be certain exceptional individuals) a few times over the years (since I saw my first one in 1984), but I find them to be stunning, especially when you factor in the huge dorsal. They also have a color edge along the dorsal. Here's a decent example - http://www.tropicalfishfinder.co.uk/dbimages/glyptoperichthys_gibbiceps_adult(1)(1).jpg