Closest thing to a "unicorn" I really want to be old enough to hunt for is a Sig Sauer P228, it is such a cool gun, of course, there is always the option of a 9mm P229 instead.
Those are the ones that hurt. The ones that you know exist because you saw them and had a chance (of a lifetime it turns out).
In 1980 I saw a new Browning skeet model 20 gauge with a receiver that was lavishly engraved and color cased; and the most gorgeous light wood imaginable. I could not afford it at the time. I have sought it out since. It's not even documented in the out-of-print $350 superposed book. But I know it exists because I saw it with my own eyes.