Just announced: on October 13, World of Goo comes out.
Trust me, you need to buy this. All of you. I don't know, go beg outside of Wal-Mart for a few hours or something.
It's also on WiiWare but you should just get the PC version for much superior control and resolution.
I've had it pre-ordered for like half a year and as such have gotten to play Chapter 1.
If you liked Portal and Braid, this is the next in the series of absolutely brilliant and stylish life-changing puzzling.
Buy World of Goo.
October 13.