Login sound - remove from Startup Applications and place somewhere more appropiate
As per unity-design discussion:
">I agree startup applications is not something that you would use frequently and the only item inside is the "Gnome Login Sound" (which i also believe is not the correct place for it either, as i was looking how to disable startup sound a few days ago in more logical places like user accounts or sounds but did not find it , so i had to do an online instructions search...).
Agree, that's a terrible place for the login sound - it's a hack surfaced to the user. Please file a bug.