Duct tape has been a part of my EDC before I even knew this acronym. It works great for repairing your equipment - some say if you can't fix something with a duct tape, it's not broken. It's also good for improvising stuff - while yachting I made a lot of gear with duct tape, plastic bottles and garbage bags and they worked long enough to get to port and replace it with real equipment. I put some duct tape to my PSK (which I usually don't carry, I've been stuck in a city lately) and I also carry some in my pocket (one roll is enough when I don't expect to use it - if I plan some repairs, I take more) and a lot more in the car.