Flashing back to an earlier, bright-eyed, bushy-tailed me:
Vault - So this card lets you turn all of your awesome cards into copper? Uh, good luck with that. +2 cards whoop-dee-doo. Witch does that AND it curses your enemies!
(it took me an embarrassing amount of games before I figured out that Vault will always get you Gold, and that Vault + Gold will always get you Province)
Loan - Paying 3 for a copper?!?! Are you serious?!?!
(I've now logged games where one Loan has killed 5 copper all by itself... still a junky card most of the time, though, I think)
Mine - Wow this card is so awesome, I better use my extra Buy on Copper so it won't run out of targets!
(no comment)
Thief - OK, it's kinda mediocre on its own, but if I chain a bunch with Villages and Smithy...
(in my defense, I learned pretty quickly how horrible this idea was)
Nobles - OK, I'm no chump anymore, I know that Village + Smithy is kind of meaningless, but Nobles is a self-combo that gains you victory points!! Nobles all the way FTW!!
(learning moment: I ran out the 8 Nobles pile all by myself vs. an opponent who was already up to 6 Provinces & did the math - I'd need 2 Provinces and 3 Duchy to catch up, all on a single Buy per turn. I did not win that game)