Quite a few manga have some rather great art but I couldn't read much of it because of the story - let alone remember the name. A few mentioned here I do agree with though. Black Butler for one. I tried to get into it but it didn't work for me.
Originally I loved Death Note... but I couldn't watch the anime - it moved too slowly and just seemed off to me. I can still read the earlier books - I find them interesting - but as the series progressed I lost a bit of interest. Especially after certain significant events.

Biomeat Nectar is one that doesn't have the most pleasing art but a story I love. I've read it a few times. It's a great apocalypse-type story.