People being born with dual-activated bodies

[APeacefulWarrior]

I have an ex with a weird variation on this: She could see into the ultraviolet. To her, blacklights were a bright white-indigo, rather than the dim glow most people see. This also was true of things glowing under blacklight; they were far brighter for her. In fact, when I found a picture of a blacklight room that looked, to me, very close to how most people see blacklight, she was actually surprised at its appearance.

The downside? It hurt like hell. Seeing a blacklight was apparently like having needles stabbed into her eyes. Even the tiny little ones which have become popular to use as Christmas lights.

So, basically, worst mutant superpower EVAR.