1) Writing out the word "Ummm..." Cute, but too cute by half.
2) Using the expression "too ____ by half".
3) The term "nonsense on stilts". Unless you're referring to a French mime playing a banjo while walking around on actual stilts, knock it off.
4) Expressions reduced to letters, like "ROFL" or "LMAO". Unless you actually write out "Rolling on the Floor Laughing" it's pretty safe to say you are not in fact on the floor, writhing in guffaws, attempting to type.
5) Referring to your opponent in an argument as a "basement dweller". We're cubicle dwellers, dammit!
6) Using the terms "Dimmocrat", "Rethuglican", "Teabagger", and "Nobama" to refer to your political opponents. Name calling? Are we not beyond that? And yes I know the other guys do it, but we should be beyond "they do it too!" as a counterargument.
7) Related to this, if you call someone a Nazi, they'd better actually be a disciple of Adolf Hitler. That guy trying to cut taxes on the rich or expand health care coverage for the poor is not a Nazi. Or hell, maybe he is, but not by virtue of those positions which are pretty mainstream.
8) Posting photos of your enemies with their worst facial expressions. Yes, that looks like Hillary was about to eat a live rat. But if someone followed you around with a camera all day, they'd get some choice shots of you as well.
9) Intentional misspellings do NOT have to go--"vodak" and "fambly" are still perfectly acceptable.
10) Posting video when text will do. Annoying dude!