Maybe it's not a big secret, but so far every single game that I've played where Changeling has appeared there has been some cute trick that you could do with it.
Silver gainers
Hard-to-purchase Alchemy cards
On-gain effects for cards you don't actually want (IGG FTW.)
Careful with Blessed village, though. If you get any of the gaining boons, they cover up the BV and the lose-track rule means you can't exchange it for a Changeling.