Here in the NYC area, the dollar coins (Susan B. Anthony coins from ~1979) and the more recent Goldies come from some transit card vending machines. Oddly, those same machines don't accept them. A few years ago, I used one of the Suzies at a store and the clerk thought it was a quarter. The clerk was not some 20-something who might never have seen them but an older woman who might have remembered them from 30+ years ago.
I think those old Eisenhower silver dollars would freak out store clerks of any age (I have a bunch of them), as would the Kennedy half-dollars (I have them, too), neither of which have been produced since the mid-1970s. I have a few 2-dollar bills but some of them, I once heard, are valuable if they were those "mistake" ones whose image of the Declaration of Independence was not done correctly(?).
I'd still like to know how to exchange any of my Canadian coins (quarters and lower) I have accumulated over the years for US currency without going to Canada. Banks won't take them, only paper currency (maybe the dollar coins?). Or, I have to find someone who is about to visit Canada.