I know many people have already said Tali, but I would like to share my experience. As soon as I met her in Mass Effect 1, I thought, "That's the one I'm going for." since I already knew that it was possible to romance characters. The way she is, at first, kind of an outsider who's different and doesn't really fit in with others(something which I'm sure a lot of people can relate to, judging by the number of Tali responses) was something that I liked. I like shy girls, OK? I was mighty pissed when I found out that you couldn't do anything with her, but then overjoyed that you could seek a romance in ME2. While she's not as shy as she was before, she is still getting used to being with others and acts a little awkwardly around Shepard, which is always cute. I especially liked the way that she SPOILER ALERT caught Shepard before he fell at the end of the suicide mission, which I know changes depending on who's in your party, which she was.