It definitely depends on the recipe, but I have seen a handful of baked goods where they swap mayo in for heavy cream(in greatly reduced amounts) for more density and moisture.

Sometimes an odd-looking substitution works. Like instead of milk, I use cream cheese in my mashed potatoes. Makes a denser mash with a slight tang to it, goes great with things like a nice kielbasa or as part of a filling for perogies.

EDIT: I just can't fucking spell, and have no clue why my phone didn't catch "recipie".