Liara, she's the perfect example of the hot alien girlfriend sci-fi loving heteros (and lesbians) are supposed to fantasize about. My evidence:
1) Lives for a thousand years, will always be hot during your life.
2) Low enough self esteem (initially) to be attracted to the most socially awkward nerd alive.
3) Chooses whether or not to reproduce during sex.
4) Can have sex with you basically in your mind, an experience suggested to be far better then boring old human/human sex. This also implies even if I was a quadrapalegic she could enter my mind and we'd be going at it like animals.
5) Can reproduce with any gender so anyone could have biological children with her.
6) Can use biotics to kill your face (or anyone else you need).
7) Is both blue and hot, isn't this one enough?
She was basically designed in a way that almost makes me think of a cheesy old sci-fi movie about Venusian Vixens. She was created to make you attracted to her without her outright raping you. She's the only one that will make a pass at you in ME1, Shepard has to kick things off with one of the other options if you want to go that way.
I'd even say they went so far as to make the other romance options kind of douchey in ME1. Kaiden is a wiener and Ashley is only slightly less horrible then Kaiden.
