Mine story is pretty under-whelming - its a 1977 Honda XL175. I got this bike in 1987, through a round-about process, but it was my first bike (and my first rebuild, now that I think of it).
It got flogged to hell and back - drowned, jumped, over-revved, crashed, neglected and generally treated quite poorly. Eventually, it becoming a problem child due to having both a slipping clutch and stripped kick-starter splines (think about it).
As a late teen I sold it for $50 to a mate. He on-sold it to another mate for $50, and I'm pretty sure it got burnt in the bushfires of Xmas day 2001.
Of all of the bikes I've sold since, it would be the bike that I'd love back. Yes, I know that it was a flogged out old paddock bike, but I still wish I had it.