Villa + Watchtower
Let's you play a bunch of treasures, use $4 for the Villa, and continue to draw your deck.
Note all of this is theory from a novice player
Villa + 'Draw-to-X'Seems like there might be some pretty strong synergy between Villa and all the 'draw-to-X' cards. Obviously disappearing villages and 'draw-to-X' go well together, but Villa also lets you empty treasures out of your hand without your turn truly ending. In addition each 'draw-to-X' card has some individual synergy as well.
Villa + WatchtowerIf you can get enough coins with a Watchtower in your hand, you can buy a Villa and another card, and then play all 3.
Villa + LibraryPlay Library -> draw a hand with treasures and a single Library, discarding other actions -> Buy Villa -> Play Villa + Library and draw through your treasure-thinned deck
Would work especially well with Estate trashing
Villa + Jack of all TradesBuy Villa to get all the treasures out of your hand. Play Villa + Jack. Repeat if you draw another Jack. Villa + Jack can handle extra treasures as long as there are Villas available. Being able to draw through so many cards and play early Jacks makes this strong for Estate trashing as well, which is good because Villa + Draw-to-X is hurt badly by victory cards.