My five favourite traits by far:
Over Emotional for the huge happiness boost as it generally keeps my happiness bar at full.(Thanks Carl!)
Loves the outdoors for the epic +20 mood boost outside which is amazing for any sim.
Ambitious for the extra LTH points and also a small bonus is that it helps people going for careers. my only complaint about this trait is that every now and then you get the anxious to advance moodlet but I suppose that's nothing the moodlet manager can't sort out
Virtuoso- not everyones cup of tea but I'm a big fan of self employed musicians *cough* performances abuse *cough* and this trait gives you an extra master track (although on my guitarist I got 2 ballad of the raider master tracks, is that normal?) and no sim can call themselves a musician without it.
The last trait really I couldn't decide on completely.
It's probably out of charismatic and green thumb depending on whether I can be bothered to do gardening.