Okay, I just noticed this thread.

I actually had a bit of fun a few years back following sole first-uppers in fields of 12 or more and particularly in races of 1300m+.

By the way, on a similar note, you could also take a look at sole first starters. By that I mean, the only horse in the race which is having it's first career start. Again fields of 12 or more and concentrate on maidens.

Don't think it's any holy grail or anything, but it's not bad for a bit of fun or perhaps include these horses in multis.