Jake! (circa 1850s)
::scratches his head:: Bogans??? Top tucker??? I’d ask for the origin of these words, but I’m sure you aussies would only end up confusing me more 
Every once in a while, I get a wild hair, and go for the old fashioned “Stupid Fly”.
i.e. “That car is stupid fly, yo!!” 
Also, I’ve become increasingly fond of ‘dope’ lately (not to be confused with drugs).
This is all very choice (I hear they use that a lot in Utah).
Interestingly enough, back in the first half of the 20th century, gross meant “good”…
But I’ll show I’m a child of the 60s by throwing this one onto the ring:
BOSS!
Ha, I beat SPOOFE to
“underpants”!
Wow, thanks for the correction on “pants”. Imagine how red my face would be if I called something “pants” when it clearly wasn’t!
Another few… “tight” and “strong”. Tight is pretty hip with the game geeks. Strong is one I’ve heard from a carpool mate of mine.
I use cool, neat, or impressive. Awesome I reserve for when I experience actual awe. Bad means I don’t like it - Phat and Gear? Give me a break. One isn’t even a word and the other makes no sense.
Nonny
I like the old expressions.
They’re the bee’s knees, doll.
Ok, I can understand how beaut could mean good (though that’s not the context I’ve heard it in before) but how could ripper mean good? In your example it seems to be a noun…
I like to use “Kicks” as in “That kicks! [butt]”
[Monty Burns]
Excellent.
[/Monty Burns]
I can help with the Bogan part…
Bogans are usually guys in their teen to twenties, who customarily go about in black boots, skintight black jeans and a black tshirt with a packet of smokes either tucked into the sleve of the shirt or in the top pocket… they tend to be the “tough men” and are mostly foul mouthed people 
I was never that skinny to make the jeans look good 
bangin!
Tits, cups, scrumtrulescent
We say “sweet,” but we say it in Hoosierese: “Suuh-WEET!” Sorta like you’re calling a pig.
If someone is conceited, some of the kids tend to say she thinks she is “all that with bisquits and gravy on the side.” Because, for some reason, “conceited” is too hard to remember. Go figure.
I say “cool beans,” much to the cringing humiliation of my sons.
k
I feel that the word “neat” is the right combination of nerdy and nifty for me. This is assuming that you define “nifty” to be the right combination of nerdy and “neat”.
Think that five times fast.
Tubular!
From the East end of London, England:
The Dogs Bollocks!
Pucka!
Sweet as a nut!
Sorted!
plus many more that i cant recall at the moment.
Pants=good? I subscribe to the Homer Simpson view of pants: “Don’t you hate pants?”
Okay well, I used to like saying, “Evil.” you know…someone would say, "I saw a great movie the other day. “Evil.” I never really used it much but I’m going to try. I know it’s not a real slang but I think I can try to make it circulate into colloquial use. So remember, it’s not cool…it’s evi.
I was taking a ceramics class last semester, and one of my classmates was this hippie-skater guy named Brian. He was unloading some pots from the kiln one day, and he got all excited when he pulled out one of his, but I couldn’t tell if it was good-excited or bad excited. The glaze on it was kinda funky, the kind of thing some people would love and other people would hate. He shows it to me and says, “Dude! Check this out! That’s sick! That’s bad! That’s fatty!” I’ve never felt so old in my life; I had no idea what he was saying. I just nod, and say something along the lines of, “It sure is!”
Turns out he really liked it. Sick, bad, fatty. O-kay…
“Fatty” was Hippie-Brian’s favourite slang-for-good word; he used it all the time. I think it’s drug slang. The rest of the class kinda picked up on it; I swear I even heard the prof say once, “That’s kinda fatty.”