Metroid Prime ! Just got the 'cube last week, and enjoying every minute of it. Though because of a series of stupid trivialities I haven't been able to pick up a memory card yet
So I'll just have to keep playing the Derelict Space Station and bits of Tallon Overworld till this weekend or so
Still, MP = coolness. I can see why it got about a 95 percent average in the reviews =)