Two cards stick out at me here: City and Junk Dealer.
Everyone knows how awesome level 3 Cities are. They're amazing. And Level 2 Cities are great too. But how often do you see them? Level 2 you probably see pretty often, but it's rare you can properly balance adding a lot of village+labs to a deck that previously didn't have them, without suddenly having a lot of wasted spare actions - so often, I find, it's only marginally better than a lab, which you can only get late. Level 3 cities are even rarer, and it's unusual you play them for more than 2-3 turns. Yes, if the game is working towards them, you need to either end it quick, or split them yourselves, but I find those situations are increasingly rare, especially when playing with all expansions, lowering the chance of colony games to about 1/5 (given City is in the game).
Junk Dealer, on the other hand, I find myself considering, and almost always buying, in just about every game it's in. It's an extremely nice card, giving you continued economy while trashing anything and everything. It's great in cursing games, and against top deck attacks (early on at least). Obviously it has weak points, but it's seemed like an extremely strong DA card in my experience. Ironically I actually put it 38th on my list, but I'd probably shove it up to top 20 now.