Presents being given for the sake of giving presents and ostentatiously expensive presents. In relation to this: the way FiL virtually throws the presents at you as though there's a time limit for opening them. Oh and age-inappropriate gifts for small children. Wouldn't be so bad if he were too young for it, but a 15 mo does not need a rattle especially not as he has already received two from you on other occasions
Novel varieties of traditional Christmas food - I don't want pine-scented icing sugar on wanky mince pies you got from Waitrose, thankyouverymuch. 6 for a quid, eat them cold without anything else.
Plastic Christmas trees that (look like they) are bought predecorated. Why do you want to look like your tree was stolen from the local shopping centre.
Eating Christmas dinner in the middle of the afternoon. Just why?
God, this is making me realise that all my Christmas irritations are connected to FiL...