My younger brother (16 years younger) used "leet!" sometime back. When interrogated he said it was short for "elite" and is spoken mostly by hardcore gamers when speaking of something that is super-cool or shows a great deal of expertise. "Leet" and "Newb" have replaced "Hip" and "Square"?
Then there's always:
"Rad", "Tubular", "Awesome", "Phat", "Excellent", "Dope", "Bad Ass", "Gnarly", "Slick", "Nifty", "Neat-o", "Bitchin", "Rocks", "Singular", "Wondrous", "Wonderful", "Astounding", "Straight", "Tops", "Preeminent", "Sick", "Righteous", "Fantastic", "Marvelous", "The Greatest", "Slammin", "Dandy", "Super", "Groovy", "Uber-cool", "Unreal", "Diggity Dank", "Beyond Belief", "Stupendous", "Money", "Kickass", "Crump", "Cool Beans", "Terrific", "Two Thumbs Up", "Intoxicating", "Man!", "Beast", "Marvelous", "Astonishing", "Amazing", "Scrumptious", "Mean", "Hype", "Fabulous", "Superb", "Fresh", "Primo", "Tight", "Fine", "Kickin", "Decent", "Grand", "Tits", "Glorious", "Divine", "Fabulous", "Sensational", "Hot", "Splendid", "Keen", "Nifty", "Dandy", "Ripping", "Super", "Marvelous", "Swell", "Tremendous", "Dreamy", "Exceptional", "Splendid", "Beautiful", "Niiiiice!", "Mint", "Stellar", "Hot", "Tricked", "Killer", "Choice", "Clean", "Fly", "Cherry", "Alvo", "The Bomb", "Butter", "Far Out", "Hella Cool", "Remarkable", "Extraordinary", "Horrorshow", "Ill", "Jiggy", "Kosher", "Copasetic", "Magnificent", "Off The Hook", "Spiffy", "Pimp", "Ruley", "Wicked", "Dynamite", "Out of Sight"
I guess I'll just stick with plain old "cool".