SeanBateman's 'MWhaling, what do you think of QC' thread in the Fish forum got me thinking about why I like the webcomics I do.  Is it the art, the story, the jokes, the characters, etc.  So, post about your favorite webcomics.
Art-wise, my favorite webcomic is 
http://www.stuffsucks.com.  I love Liz Greenfield's monochromatic artwork and how it adds to the story and characters.  I also love the style in how she draws the characters and other stuff.
Story-wise...that's tougher.  I love reading through the QC archives, and up to oh, 470, 480, it was probably my favorite comic story-wise.  But something changed after that, and I still love the story, but it's no longer my favorite.  I don't even think the 'someting' was the talk Faye and Marten had, it was something in how the tone and style of the dialogue changed, I think.  Anyway, I found myself being more and more attracted to comics that have set character and snarky dialogue, but perhaps a looser storyline.  I love Pennt Arcade and Ctrl-Alt-Del, as well as Diesel Sweeties and Overcompensating.  i love them for their characters, jokes, stories, and randomness.
Character-wise, QC probably still reigns supreme, but Stuff Sucks is definitely gaining.