1) Having a cold when a song like O Come All Ye Faithful is on the radio.  I was in a children's choir for a year (soprano!) and loved singing that song, so I try to sing strongly.  And hacking cough follows hacking cough.

2) That hideous Christmas Shoes song.  There is nothing redeeming about the over-saccharinized self-celebration of a shopper loaded up with gifts (capitalist crack?) helping someone buy a pair of shoes and feeling like a hero who's done his duty.  The music's bad, the lyrics/story possibly worse, and the message is confused at best.  And stations seem to want to get a year's worth of playing time into one month.

3) Having to work when most of the office is gone.  It's a good time to learn just how interrelated a company's work is, when 75%'s vacations cripple the remaining 25%'s productivity.

That said, Merry Christmas and/or whatever holidays you celebrate!  Hopefully everything beyond these 3 annoyances is just plain fun.