Animal Crossing Feng Shui
I've always admired Animal Crossing more as a concept than as an experience. That is, I find the idea hugely fascinating and am glad it exists, but I didn't particularly enjoy playing the GameCube version a couple of years back. I knew as I was playing it that I was much too goal-oriented, and not playing it 'right' but still... I never got into it. (The static facial expressions turned me off to a surprising degree.)
But I always enjoyed the MMO-ish massive exploration side of things. Do X in location Y and Z happens. Perform A on national holiday B and you will see C. It has, to me, a genuine feeling of mystery, of stuff you may be able to discover that others haven't found, much like Elite, or even World of Warcraft (databases such as Thottbot and Allakhazam notwithstanding).
So imagine my utter delight when I found out through DS Blog that Animal Crossing for the DS has a functioning Feng Shui system. Place your stuff right, and your luck increases and better stuff drops off trees. This has to be the coolest feature in a game since... since... um, I'll get back to you on that one. For all I know it's an elaborate hoax, but it's still cool.
I assume it doesn't, but it would be even cooler if it actually modelled the dragons and chi and what have you of the theory behind feng shui, and you could properly interact with it, and no-one had noticed this until now... (kind of like finally getting to see that Emerald Dream those nightelfs keep talking about).