100 mph tape, aka 90 mph tape, aka Army green tape. Works well in a myriad of circumstances. Mended clothing, made ersatz knee pads so I didn't have to mend clothing, fixed rucks, many other uses. And yes, it can be used to patch rotors on helicopters - as told to me by a very senior MW5 who had done so.

If I had my druthers, I'd use Gorilla. Hasn't failed me yet, but I don't own leather luggage.

I do own some silver duct tape. It's like the Force, it has a dark side, a light side and it holds the universe together.