What downloadable Wii game have you enjoyed most?

Can be either WiiWare or Virtual Console. Whatever.

So tell me: what has been your favorite downloadable Wii game so far? And if technically not your favorite, what downloadable Wii have you returned to or played the most?

As for me, I gotta go World of Goo all the way. Yes, even more than anything else on Virtual Console. Although I have played a lot of Dr. Mario X with the wife.