To be honest, the called shots in R&G are universally pretty crap. Even at half the penalty I'd avoid using them.
I actually have two stories that made good use of the the location Called Shots, one funny, the other tactically effective.
The tactical use actually was told me just last night. The team was being attacked by a powerful awakened individual wielding a sword. The team Sniper took the first attack to Called Shot for the Thigh, and applied the Winded effect. Winded makes it so that the target can't take Complex Actions for a set number of combat turns. So the melee weapon becomes useless as they can't make any attacks with it.
The more humorous story: We had a slight misunderstanding, and one of the magicians became upset (basically, man makes a crude joke, woman reacts harshly) and cast Levitate on a teammate (the one who said the crude comment). Presumably, this was the equivalent of pushing him away, but with Magic. In turn, however, he gets startled, because now he's floating and can't get down. So the teammate draws his pistol, and shoots her in the foot. He was able to stay collected enough to aim for a non-vital area. The rest of the team jumped in afterward and separated the two and calmed things down, but still kind of funny with the series of escalations. It was literally the sort of comment that could have been responded to with a slap across the face ("how dare you" *slap*), she just decided to resort to magic instead.
There are definitely times and uses for the Called Shots. Honestly, at my weekly table, few of my players ever use Called Shots at all, let alone the extra ones in Run & Gun.