Definitely Mario Maker. I've been into Lunar Magic for a long time now and having an official Level Editor is just all sorts of amazing. I love creative editors in games, be it platformers, racing games or even RPGs (PC FF VII <3). Hell they should've made an Ace Attorney Case Maker (I know there are fanmade ones). It's one of the main reasons why Warcraft III is one of my absolute favorite games of all time. I don't know if I even played one regular match, I was too occupied with playing funmaps and creating them.

Super Smash Bros and Mario Party 10 too of course. And I'll probably get Angel Beats! 1st Beat sometime this year. ...depends on how quickly there will be a fan translation (I WILL get and play through EVERY game Key puts out). I'm also guessing Higurashi no Naku Koro ni will appear on Steam sometime this year so I'll get that as soon as it appears, too.