Oh, many things irritate me. I can think of a few now.
My mother really patronises people who work in shops, etc. She over-gesticulates (exuberant hand movements) to people when she is speaking to them, as if they are retarded or as if English is their second language. It really gets to me.
For example:
"DOOOOO. YOOOOOO. HAAAAVE. WUNN. OVVV. THEEEEESE."
Pisses me off. Rising shop prices also irritate me. Long list, but I will stop right now...