Some things that bother me...
1) Incorrect use of "take" and "bring". You bring things to where you are, and you take things to where you aren't. You might bring something here, but you'll take something there. Come and go work similarly.
2) Using comparative/superlative incorrectly. Especially latter and former. In a list of three or more items, the one that comes at the end of the list is the last item, not the latter, and similarly, the one at the beginning is the first, not the former. Additionally, "superior" is a comparative. "Supreme" is the superlative.
3) Fewer and less. They're really not that hard. Fewer is used with plural nouns, and less with singular ones. Same goes for fewest and least (though make sure you're not making mistake 2) and much and more. Yet so many people get it wrong.
I could probably go on for quite a while about these, so I'll just link to this.
http://tvtropes.org/pmwiki/pmwiki.php/Main/TheBigListOfBooboosAndBlunders