The grave mourning, the water drinking, and the trolling drive me nuts. In one household, every day I'd come home from work (one of the active careers) and the child was on the computer trolling. It was her go-to action if left idle. Her trait was loner, which I think would be neutral as far as pushing that action.
Sims eating snacks like cake or something as meals also bugs me. "Oh, I need to go to work and I'm starving. Sure, there are full meals in the fridge, but let me eat this cake that will fill only a tenth of the hunger bar so I can get stuck at work ravenous within an hour, and in a bad mood because of it."
Also, ghosts that brew tea and leave puddles on the floor, and haunt the shower just to break it. I think they just have an affinity for watery messes.