Rating: 4 / 5
Inov-8's Debrisoc is a sock with a short built-in gaiter to keep crud out of your shoes. I have the Coolmax version; they also make it in merino.
I really like them: wore them for several days hiking in very muddy Alpine foothill forests, after loads of snowmelt and a rainy spring, and had comfy and stone-and-twig-free feet the whole time.
(Mine came with both socks marked as "L": I didn't notice immediately, and they fit my right foot perfectly ok, so I didn't bother querying or sending them back)
+ superbly comfortable sock
+ coolmax version dries quickly (sock part)
+ crud-free shoes; gaiter part stays in place well
- gaiter part is slow-drying
- combination sock & gaiter maybe less versatile than separate items
(This really should be a 4.5 - the minuses are rather minor)