There are some products which are quite obviously animal-derived (e.g. leather), but there are a lot of others where it's much less obvious (e.g. tallow-based soap).

What are some of the less obvious places people might find animal-derived ingredients/products? Also, if you know of any good substitutes or alternatives to those, give your recommendations as well!

Meta note: wasn't sure where this would best fit in on the site, but I figured ~enviro is a good fit. If it needs to be moved to a better home, feel free!