The strangest expression that I've ever heard is, 'that's as bad as two ducks and a dream.' My grandfather always used to say that, and it always confused me as to where it derived from; I was too young to ask.
'How did your horse fare, Grandad?'
'It went as bad as two ducks and a dream, cricket.'
Contemptuous soubriquet that I hear a lot at the moment is 'major league a*shole' and 'plastic-ass-man.'
I've wondered about expressions too, it's a very interesting minefield; I don't think it's down to age, but rather down to character. I use rather antiquated English, with all the rules left in, and I sometimes make up figures of speech and proverbs when I can't think of anything else... but no, I don't really use 'cool' that often, I tend to use 'fantastic' or 'great.'