Winehiker offers his distinctions.
My list is about the same as his. If I plan to be out all day I try to take along my water filter … it’s saved my fanny on many a hot summer hike. I also toss a little silnylon tarp in the bottom of the pack, like a bit of insurance I hope I’ll never need.
A commenter mentioned water bladders — every one I’ve ever had has sprung a leak, either from material breakdown or me forgetting to screw the lid on all the way. It’s a nice but-cooler on a warm day hike but can take all the fun out of a camping trip. I use one on all-day hikes but I’d prefer to just carry water bottles.
I like a water bladder but I’m having the same problem you mentioned of leakage. I even resorted to putting the bladder in a heavy plastic bag and the bag leaked also. If the bladder weren’t so handy I would go back to bottles. On the other hand I lost a water bottle on my last trip.
I have several 3 liter Camelbaks and one of them sprung a leak after I washed it on the inside with the Camelbak cleaning brush. I figure one of the bristles on the brush must have poked through the thing while I was scrubbing away. I slapped the sticky part of a bandaid over the leak and it patched it right up and the thing has not leaked since. And I’ve stopped using that cleaning brush opting for soaking methods of cleaning instead. And I have not had a problem with leaks from any of my Camelbaks since (knock on wood).