shotgun
I've put a set of fiber optics on a turkey shotgun, from the Williams Co I think. Considerably more visible, especially in dim light, than any standard bead and groove arrangement.
My rig has two green dots on the rear leaf, and a red dot up front, and I like the contrast. I was a bit concerned over how durable they might be, after all, they seem like simple plastic tubes. But they have held up over moderate to heavy use in 3 seasons now, both me and bamaboy hunting the gun some.
FO sights are pretty common on handguns as well, several guys in my local club have them on IDPA and 3gun rigs, and woudn't shoot anything else. Every once in a while one will loose a pipe (3gun is rough on gear) but many rigs have replaceable pipes.
big difference for 50 something eyes!