Little known useful items

TIL that the enchanted red topaz ring exists, it allows you to damage vampires without silver weaponry but for half the damage, which is terrible. But it also increases the max hit and accuracy when using silver weapons on vampires. This works on the sotf boss to give the same max hit as the b-ring(i) with a 15% accuracy increase. Is there any little know or forgotten item with a niche you know about?