Warm clothes generally! Pyjamas specifically. I've just been pj shopping in Next and came out with mens bottoms which are a thick warm fabric, plus a black thermo top. Super warm. Gorgeous.
The womens department on the other hand, served up the thinnest, cheapest (ugliest) utter crap material that wouldn't insulate you in a tropical climate.
In the men's department, I also saw furry lined hoodies. The women's department had short sleeved Christmas themed t shirts.
MEN RUN HOT, WOMEN RUN COLD! MAKE IT MAKE SENSE.