Sealskinz Waterproof All Weather Mid Length Socks XL
Size: XL / US 13-15 / UK 12-14
These socks are amazing! I've worn this model of sock on soaking wet trail runs in the winter, through snow and slush, and my feet have been fine. I have Raynaud's and these socks solved my cold feet problem. I have worn them for runs as long as 50k and they have not been uncomfortable. They even have an Anti-Blister feature which prevents rubbing.
These socks have a Silicone "Hydrostop" band around the top (see the 3rd photo), which prevents water from running down your leg and filling the sock.
The socks are a three-layer construction for warmth, durability, and waterproofing.
I imagine you could even cut a hole in the bottom and use them as cycling shoe covers...