What is your least favorite card?
The card I spent the most time hating was Pirate Ship. There were always people convinced it was crazy broken powerful. Having to endlessly prove them wrong, with the threat of them saying "aha I was right all along, wow you really blew it" if the card was ever any good just sucked all the joy out of those games. I am over it though, people worked out just how good Pirate Ship is.
I veto Oracle the most. It just ruins playtesting by endlessly flipping over whatever new card you wanted to test.
The card I am most embarrassed by is Rebuild. Scrying Pool by contrast is a card I blew it on (the grafted-on attack part makes it less cool, way more wordy, and contributes to Alchemy games being slow) but which I still enjoy playing with.