My own clumsiness if often what irritates me on a daily basis 
With other people, the biggest irritation is not saying thank you, or even acknowledging my existence, if I have held open a door for them or, if they have dropped something and I pick it up for them and hand it back and they just take it and walk off! (With me shouting after them 'you're welcome, don't mention it' - oh, you didn't did you.)
Postmen who left post hanging half in and half out of the letterbox; so I put up a postbox at the bottom of the drive and now they leave the post hanging half in and half out of that meaning that the rain runs down the exposed post and soaks the rest of it in the box to a mush 
Anyone who answers their mobile phone during dinner or conversation with anyone else and continues to have a conversation with that caller (unless they are waiting for an urgent call which is then understandable)