Having played Dominion for over a year and a half now, I've noticed (as I'm sure you have) that there are quite a few cards that just have +1 Card, +1 Action, and then some text. These are often very powerful cards, but there are some weak ones in there as well. What they all have in common as that when we first look at them we think "+1 Card, +1 Action, murgh, this card doesn't do very much... oh wait!"
Now, for them to qualify (in my completely subjective opinion), they have to have ONLY +1 Card, +1 Action, and text. No other guaranteed vanilla bonuses. Scout does not count, since it does not have a +1 Card, and Great Hall does not count, because 1 VP is a vanilla bonus. Here they are by set:
Base: Spy
Intrigue: Wishing Well, Upgrade
Seaside: Haven, Pearl Diver
Alchemy: Apothecary, Familiar
Prosperity: N/A
Cornucopia: Hamlet, Hunting Party
Hinterlands: Scheme, Cartographer, Highway
Dark Ages: Rats (possibly others?)
I considered Caravan, but the text is simply stating that the extra +1 Card happens on your next turn, rather than, say, Hamlet, whose text dictates prerequisite activities (discarding) to get the extra vanilla bonuses.