What comics (including webcomics) have the most distinctive art?
Transmetropolitan, though I have a hard time deciding whether is it the style or the characters. Probably both.
Knights of Sidonia was drawn by an architect. Definitely shows - thel background / landscape shots are quite ridiculously good and give you the scope a lot of comics tend to miss.
The Other End Comics
Extra Fabulous Comics
The comic is very black white and has an exceptional story in my opinion.
Unix Surrealism
I personally think the art style is very distinctive compared to just about anything else I’ve seen.