According to my 16 yr old daughter...it's not cool for someone my age to say "dude". She also doesn't like it when girls/women use the word "dude".
The favorite word for my 14 yr old son & his knucklehead friends is..."pants". They just think it's a funny word. They've taken to using it as an exclamation..."What the pants?!!".
A favorite word of mine is Fizbo. It's not really a word, I use it to refer to people & it sort of replaces "dude" as in "Hey Fizbo, when are we going to the movie?" or "Let's meet in Fizbo's office." I had a boss that used the term to refer to anybody on his staff. Apparently it is a real estate term that means For Sale By Owner, FSBO. He just appropriated it to refer to anybody.
A few other irritations that I just thought of...adding "ing" to words that shouldn't have "ing" such as "efforting" or "partnering". I guess those may fall under the category of "office-speak" which I hate. Words & phrases like "repurposing" "synergy" "paradigm shifts" "incentivise" "going forward" blah blah blah.