I can't help but think that this is an odd survey. I love attacks, they are my favourite mechanism in the game I must say and without it Dominion probably would be a game that couldn't catch my interest for too long. Strong, well-balanced, attacks are yum. All love to Mountebank and Goons. The fact that many of the cards without the attack type can intervene with other players deck shows that this types of interactions are essential to the game.
Now I'm not saying that anyone here disagrees with me necessarily, I just rather want to chose which attack I love the most. (Swindler, I think.)
I chose Urchin however. I've been trying for a while to always open Urchin/Urchin and I have yet to feel that that was the wrong choice. The chance to get a salty opponent yelling about "luck" when you hit Mercenary turn 3 is rather high too. Could be without, honestly.