Like Greywinter I can't narrow it down to one, but here are some that clammoured to the front of my mind loudest:
James Sunderland & Angela (Silent Hill 2) - Excellent protagonist for a journey into one man's personal hell, and a young woman who been in her own long before reaching Silent Hill...
Kane (Command & Conquer) - Beard of awesome, bald of Awesome, awesome rhetoric, badass awesome army of awesome etc
George Stobart (Broken Sword) - Can always raise a smile, especially due to Rolf Saxon's voiceover.
GLaDOS (Portal) - Need I say more, you monster?
12 years