I like Agnes because she's a total babe with a makeover, and she's dating one of my sims and they're quite cute together. I don't even need her painting skill and nice car for that appeal!
Though if we extend the criteria to "anyone pre-made in Sunset Valley, residential or otherwise," Torgo Pendragon, the pizza boy, will always have a big place in my heart. He married my simself when I first got the game. To this day, he's probably the only guy in Sunset Valley I'd actively seek out for a sim to marry.