repetition
loud noises
things being spilled on the floor
being touched
To be fair all the above happened far less frequently before I had children. Repetition is a particular annoyance - not just me saying the same thing over and over and over and over and over and over and over and over again, but chanting, singing the same line of a song repeatedly, taunting etc.
Love them, but dear God for just 24hrs of peace....