I defiantly like the Inappropriate, Hopeless Romantic, Slob, Evil, and Neurotic traits. Oh, and the Insane trait. Reasons:
Inappropriate: I just find some of the actions hilarious, such as "Accuse Mother is a Llama". The "Kiss" one is creepy though....
Hopeless Romantic: This combined with Great Kisser and Flirty gets a husband in no time, though they do randomly try to flirt with other sims, so I have to keep an eye on them. XD
Slob: I just think burping randomly and uhh... the other thing... is funny. Also, when I have a household of fat slobs, its nice to not have to clean up. Reminds me of that show where they show a bunch of people that collect trash. (AKA "Hoarders")
Evil: I love how they like evilly and get that moodlet that they are evilly delighted that somebody is suffering... they also laugh and clap hands when somebody dies.
Neuotric: Freak Out or checking something before work is a nice boost.