I have quite a list: My biggest one is when Sims are watching TV or playing chess, etc and they wave and complain they are tired when they get the tired moodlet. Or when they wake up because they go to bed almost hungry and complain because they are hungry. For these two things, just take care of it already. It seems the Sims complain and throw fits more in Sims 3.
Paparazzi always standing outside my Sims's door, then ringing the door bell every night at 1:15 am, ghosts that "wake up" around 3 am just to watch tv for 10 Sim minutes and then take a nap, when the Sims age up the noise makers and the cheering goes on way to long and when they age up, their hair and clothes change, so you have to go into CAS to change everything back to how you had it, when the toddlers energy bar is full, and older Sims wake up from sleeping, they always want to put the toddler into the crib, it takes WAY too long to get to the top of any Showtime careers, ghosts interacting with alive Sims. I liked it better when they would scare Sims in Sims 2, almost every night the children asking for a bed time story then the child goes into the parents bed then after they go into their own bed is a waste of time.
This is just my partial list. There are tons of issues I have with the Sims 3, but for some reason, I keep getting sucked back into the gameplay.