This may sound cliche or be a response that most would roll their eyes at, but my favorite card is Jace, the Mind Sculptor. Playing Mythic Conscription during its heyday and then switching over to U/W CawBlade before and after Jace and Stoneforge Mystic was banned, I have fond memories of the card and still can't help but smile every time I cast it. Even though it's only legal in Commander and Legacy as widely supported formats, I'm looking forward to the day when I acquire enough revised dual lands to be able to bust out my playset of Jaces once again and give Legacy a legitimate shot.
So yeah, my favorite card is Jace, the Mind Sculptor.
EDIT: Woohoo, 1500th post in this contest, which means that my chances of winning will eventually be less than 1:100. Oh well, here's to sick rips off of Jace's Brainstorm!
Still skeptical on the fetchlands though.
They're only used in decks in Standard because there's not much else available.
I also believe that come Zendikar Rising, we won't see legal fetches reprinted, but we will either see reprints of the Battlelands (or tangolands, whatever people call them), or perhaps the enemy cycle of those lands, which would be weird due to the enemy cycle scry lands here in M21.
I ask because it's been my dream to add a foil Mana Crypt to my cube, but not if I have to pay out the ass for it.
Much like how back in the day when you announced that you were casting Thoughtcast with a few artifacts on the battlefield, one of them being a Chromatic Sphere, you reduce the costs appropriately to find out how much you pay to put the spell on the stack, then when you go to pay those costs, you could crack the Star to produce the blue mana you needed to help cast the Thoughtcast.
I'm not sure the same way applies here, but if my buddy has a food artifact and a Gilded Goose on the battlefield and he wants to cast Whir of Invention, can he tap the food to have improvise help pay for part of the cost of Whir of Invention and still be able to sacrifice the food to Gilded Goose to also help pay for the Whir's cost? I'm thinking yes, but I want to make sure before I tell him he can or can't.
I'm guessing a judge of Level 2 or higher might need to answer this with certainty.