Character requirement: male, any race
Depending on whether you choose to ally with the Mages or the Templars, there are slightly different circumstances under which you first meet Dorian Pavus, but eventually, he will join your party if you let him.
Complete Morrigan Romance - Dragon Age: Origins
Dorian is from Tevinter, where magic rules all, quite the opposite of local attitudes and therefore causes a lot of distrust towards him from your companions and followers. However, he's a good person at heart, charming, handsome, and a little full of himself.
His sexual preferences caused some friction between him and his family, leading to an interesting storyline that, it is said, many LGBT players felt they could identify with.
He is a sweet and flirtatious man and romancing him is a lot of fun.
Approval requirement: Yes
Difficulty: quite easy; getting his approval rating up is fairly straightforward and flirting enables him to fall for you early on
Romance storyline: heartwarming and sweet
Sex scene: yes