When you say "gear", do you mean just photography gear, or general hiking gear also?
Assuming just the former, keep it simple. Other than the camera and lenses, I only carry a CP filter, spare batteries and memory card, and some lens cleaning supplies.
As to lenses, a lot depends on what you have and what you like to shoot. I typically carry 3, a 10-22, 18-55 and 70-300 (the non-L). If I had to leave one at home it would be the 70-300.