I'm old enough to remember the short-lived "rad" phase. A truncated version of radical (as in RADICAL!!!!) it was big in BMX circles once upon a time when it came to describing bikes, jumps, tricks, crashes and the grape popsicle you picked up after a day of riding.
Then Hollywood made a movie called Rad. While the movie was pretty good for what it was, it kind of wrecked our catchphrase. Calling things "rad" was no longer rad, not since it was co-opted by some middle-aged Hollywood producer who heard his son say it one day and decided to use it as a vehicle to make money.
Instead of capturing the zeitgeist of the movement, Rad destroyed it. The popularity of BMX also dropped off (coincidence?) around that time and the kids in my neighbourhood started to get skateboards instead. Skating was more "gnarly" than "rad," and is even defined by the Urban Dictionary as "when you've gone beyond radical, beyond extreme..."
I would disagree, however because the "extreme" fad came well after the "gnarly" years were behind us, around the time snowboarding hit the mainstream in the mid-90s.
Extreme was big. First we had Extreme sports. Then we had the X (extreme) Games. Everything was being taken to extremes, and for a short while life was interesting again. But the extreme craze went too far, too fast, and it was over long before you could buy extreme-branded chips or extreme gum. Cheesy movies had names like Aspen Extreme. Extreme Ops. xXx - three times the extreme.
If a product was particularly extreme it would even be marketed as X-treme (!!!) because somehow leaving out the "e" and adding a hyphen doubled down in the extremity department.
As a marketing promotion, the extreme movement had all the subtlety of the Kool-Aid guy busting through a brick wall. The more it was used, the lamer it got.
"Sick" enjoyed a brief time in the spotlight, as did "Burly," but neither lasted long.
We were using up words left and right, draining them of any meaning before they even had a chance to become someone's catch phrase in a situational comedy. It all makes me wonder how long it took the phrase "hang 10" to go from surfer chic to T-shirt cliché.
The buzzword of today is "stoked," which has enjoyed a surprisingly long run at the top. Shaun White even used it last February to describe the thrill of winning his second Olympic gold medal in halfpipe. In fact, it's been the word of choice for extreme athletes for a long time now, and is only now starting to get overplayed. You can't buy Mountain Dew Stoked Berry (at least not yet), but you can buy the Stoked snowboard game - the beginning of the end, from where I stand.