I have read most of the posts, not all, so here's my list:
"You know", often shortened to "y'know" as a nervous tic in conversation. It is particularly grating when I hear people use it two or three times per sentence being interviewed on the radio. Whoever uses it drops ten IQ points for each use, IMHO.
"Very unique" It either is unique (one of a kind, singular) or it isn't. Very as a qualifier does not help this.
"Sucks" as a description of something bad or unfortunate. " My bus was late. That sucks. ". If people thought carefully of the origin of that pejoration, it would not be used, at least in front of children.