I carry a large square of closed cell blue foam as an insulated situpon pad. Have used it to sit under a poncho back up against a stump waiting out thunderstorms and for someplace to sit in a snow pit when x-c skiing.

I carry it in my daypack for the possibility of spending the night out tending my survival fire. Good insulation is really important.

For backpacking I like the Ridgerest pads. Thicker cushion for sleeping but much more durable than the Thermarest inflatable. (I tend to bushwhack and the pads get a bit frazzled)