Oh, good question. Tough one though. It is really hard to define myself by just one game. If I had to narrow it down, maybe Metroid Prime or The Legend of Zelda: Majora's Mask.
NNID: theRepublic -- Steam ID: theRepublic
Wii U - Currently Gaming Like It's 2014 (Hyrule Warriors) - 11 games in backlog
3DS - Currently Gaming Like It's 2013 (Luigi's Mansion: Dark Moon) - 7 games in backlog
PC - Currently Gaming Like It's 2012 (Borderlands 2) - 11 games in backlog
Mobile - The Simpson's Tapped Out and Yugioh Duel Links