@clay: You don’t care about design/layout?
Why did you even bother changing the default WP layout? Better yet, you should use a blank stylesheet.
Anyways, here is my list.
1) Colour combinations of text/background that make it impossible to read. Better yet, some people use “happy” backgrounds that will make your head spin.
2) Rows/colums of hundreds of banners, buttons, badges etc. Why?
3) Blinking text/images, argg!
4) Large colured counters w/ too many zeros at the front, who cares?
5) Splash pages. Graphic or flash, they are useless and annoying.
6) <strike>Used for visited links of hover behaviours</strike> Die!
7) Links that change size on hover and in affect make the rest of the content “jump”.
8) Word counts and click counts, these serve no purpose. If some one found your entry interesting they will most likely comment on it.
9) Valid XHTML … did you even bother to click the link yourself?
10) Long lists of links to people, place etc. on the front page. If you are really into agrgating links, perhaps, a separate section could be used for this.
11) “Custom” cursors. Especially the cross-hairs …
12) Welcome to 1990s … animated gifs and “fake” awards.
13) Graphical smileys … this one is a personal preference, but some people tend to overuse them and it really looks funny on some blogs.
14) Photomatt seems to have started a trend when he posted his code for text2image using PHP … note to people: don’t use Arial, Times New Roman etc., make sure it’s antialiased, symbols picked are just lame. That said there are plenty of free fonts out there and the infinity symbol does not need to be replaced with something lame … instead download a font “like” windings that uses images for letters.
Content wise, people can and should post whatever the hell they want (That’s the point right?). If I am not interested I will just move on. However, if the site loads up and its looks ugly/hard to read etc. I will move on almost immideatelly.