The single-ingredient lanolin balm that gets exhausted new parents through the brutal cracked-nipple phase of week one.
This is hypoallergenic, purified lanolin with nothing else in it, which is why it's safe to leave on for feeding without wiping off first. It won't fix a bad latch, so if pain is severe or persistent, that's a call to a lactation consultant, not more cream. Some parents prefer a plant-based nipple balm, and those work fine too. Skip it if you or your baby have a wool allergy, since lanolin is derived from wool.