What backpack?

I use a slingshot lowepro 102 aw it supports most of my needs ,gh3 and a few lenses ie 100-300, 14-140mm ,35-100mm ,25mm or 45mm macro and tri/mono pod depends on location and needs as to which lenses I carry ,but normaly no more than three ,the slingshot is good for quick access when needed or doing lens changes on the move ,also nice when you are in a busy town ,train station ,street and want your gear in front of you ,to stop hands helping themselves to your gear for security.i also have a peli case which gives ultimate protection but only carries the camera with lens attatched and one other lens this is the best protected and safest option when travelling air land or water ,although a bit overkill for most photographers needs, a back pack is almost essential for most camera owners ,although  if you owned a large pocketed rain coat you could hold a few a lenses and camera ,although not practical on warm sunny day.