Penny. Not because her events are good (at best, they're mediocre. At worst, they're the George event), but because her about town dialogue and her married life everything. I initially married her in 1.2 because she you get punished for not getting married (you still are, but 1.3 added Krobus and he lets you slightly dodge that) by locking you out of a stardrop, and I found her the most inoffensive option. But I ended up really liking her.