The Dakine Apex was designed for mountain bikers (free riders/ downhill) and is nearly indestructible. I originally bought it for mountain biking but it is such a good day pack I use it for everything.
I take a radio scanner so I can hear if anyone is about with radio's and to get any news I may need, other then that I don't really take much, I don't even take a tent, just a Bivvy bag.