I borrowed one of the company Jeep's a few weekends ago. I spent probably two hours trying to get the stupid locking gas cap off. I didn't want to use too much force (not my vehicle, hard to explain to the boss, etc.), and I eventually just gave up and left it parked in my driveway.
The guy here at worked yanked it off with pliers. It did not do any damage, and it's been replaced with a normal gas cap. Because those locking ones are a pain in the ass, and gas thieves evidently just drill holes in the tank.
Now I want to borrow the Jeep again.