During a wet, muddy day out on maneuvers with my ROTC detachment, a stick ripped my pants from the knee to the crouch. We were miles away from where we were camping and did not plan on returning until that night. I grabbed my green duct tape and proceeded to repair my pants. Several people even commented on my creative camouflage. I'm an outdoor video producer and I've used duct tape for everything from repairing a tripod to binding a pack strap.
Nobody wants their equipment to break, but duct tape is cheap insurance.
Our best and worst backpacking trip was last fall in Porcupine Mountain State Park, Michigan. Half way through our week-long trip the soles of both boots came loose from the heels all the way to the balls of my feet. Luckily my backpacking buddies JB and Matt came through with duct tape and nylon packing tape. Every morning they'd duct tape the end of the soles to the heels of the boots, then nylon tape under the arch and across the laces. That also meant each night before getting ready to relax for the evening, I had to cut my feet out of each boot, but it worked great.