well out of the choices you've given, and discounting that some characters are not video-game only characters, I would have to say none. Some of the games I didn't play, rest of the games that I have played, there's not much to go for main character. (gordon freeman for instance, HL2 is a great game, but gordon as a character, sorry, not in my book, valve built his character by gordon not speaking a word through all the games and other characters putting the words in his mouth. I would say Alyx is probably a far better character from HL2 than gordon)
If we consider games outside of your list, I would have to say probably HK-47 (KOTOR) and Geralt (witcher) are the most memorable and unique characters.
and if we consider the other sources besides video games, then wolverine will be at the top of the list any day