Recently, I was screwed by my big box of cables, when I pulled out a SATA power connector for my modular power supply, and learned very quickly that though the ports universally fit across modular PSUs, the pinouts are not actually intercompatible, and you can and will fry your hard drives. I didn't know this; I had foolishly assumed that SATA power connectors were standardized on both ends.
That's an expensive mistake to make, though frying your HDDs is usually a lot cheaper than frying your GPU.
It's seriously annoying that this is the case though. Unless you kept the cables in the original package or in a labelled container, you cannot safely use them again if you owned more than one modular PSU.