I know spiffing, but it's very British;
You'd expect to see it in, for example, public school stories featuring Billy Bunter and those of his ilk.
'Wizard, chaps! Spiffing japes. Cripes! *Cavy. you fellows, Old Squelch is on the prowl.'
I don't think anyone ever spoke like that, at least not in the real world, but it's certainly to be found in P.G.Wodehouse and other novels satirizing upper-class twitteries.
*'cavy, spelled various ways; supposedly schoolboy slang for 'Watch out! Be careful! Take care', from Latin 'cavere'
It survives in the phrase 'caveat emptor ' - 'Let the buyer beware'
