Hamlet and Festival are my favorites. They give you +Buy, and introduce interesting tradeoffs (lack of card for Festival, hand management/discarding for Hamlet) that are sometimes drawbacks but work beautifully in "draw to X" and Menagerie engines, which I'm particularly fond of.
I still think Bazaar is mightily underrated, too; and I'm quite fond of Farming Village's defensive capabilities, even though I know it's not objectively the best Village out there.