Paint splatters
Swoosh logos
People who blatantly rip off Apple's centered-tab-menu web layout
Rounded corners (I go back and forth on this one every year or two, kinda like pleated pants)
Trying to manufacture a modern/minimalist aesthetic just by using Futura (or if you're a total ******, Century Gothic)
Actually speaking of fonts, and this might more be not-so-favorite-n00b-design-cliché but I'll include it anyhow... any of the following fonts: Bradley Hand, Brush Script, Curlz MT, Papyrus, Rage Italic, Trajan, Viner Hand, Zapfino
Small caps (eeuughhh)
Obviously standard layer effects
Wet floors 🙂 (thanks for that, I had just always thought of it in my head as "the web 2.0 reflection thingie")