Lara Croft, without a shadow of a doubt.
She was the first public attempt at a strong female character (Samus wore armour), and whatever you think of the games, you have to notice that she has two movies, nine games, an extremely long comic series, and is recognised as one of the 'faces of gaming'. This suggests that there is something behind her which makes her something extra.
Why yes, I am new here, will this start a flame war?
Seriously though, Tomb Raider III was my first game ever, and without the character of Lara Croft, I probably wouldn't still be gaming today, and in my opinion that makes her the best.