I use a Rapoo E9080.
My main reason buying it was its size. I work a lot out of the office, and these times often find me outside my home. This means my keyboard is in my bag wherever I go. It's thin and small, but not too small.
Initially I liked it having a touch pad / numeric pad combo (you can switch between functionalities with a swipe), but it often bugs me now (sometimes I accidentally tap it with my right pinky when pressing Enter). Also, having my trackball in my bag makes it unimportant. This means that on the long run I will switch to another model, although I will probably stay with Rapoo.