Off the top of my head...
-Sniper Wolf (Metal Gear Solid)
Probably my favorite character from that particular game series, she just has this whole feme fatale allure about her that just draws me, and that voice! Mmmmmm....
-Holly Summers (No More Heroes)
I don't really know how to describe what really draws me to this character but she manages to be the solitary character from that game I would ever want to even be in the same room with, let alone the same bed!
-Para Medic (Metal Gear Solid 3)
She seems like the kind of girl I would want to date in the real world, she's cynical but caring, cute as hell, and we'd be able to spend our first date back and forthing about Godzilla trivia for hours!
-Tali (Mass Effect series)
For me, the fact that you still couldn't romance Tali as a girl in Mass Effect 3 was far more disappointing then the ending ever could have hoped to be.