Generally speaking, if my gut tells me it's okay, I let strangers shoot my guns, except a couple 'heirloom' guns if I brought them.
Just lately I've had at least one person per range visit strike up a conversation and I've let them shoot at least one of my guns. Maybe 5 times in the last couple months. The most popular guns asked about so far have been (in no order): my Shield9, M&P9, Para P13, Ruger GP-100. The GP-100 might be the most popular. For some reason revolvers seem to be fascinating to the newbie shooter. At least at the indoor ranges I frequent.
I usually let them shoot a whole cylinder of .38 spl, maybe two. With the semis I usually let them shoot 10 rounds (obviously with the Shield an 8-round mag). I don't let them load/unload any guns though.
Interestingly, when strangers shoot one of my semis, they shoot the one mag and immediately put it down/hand it over. With the revos they'll usually grin, and want to talk about it. If offered, they'll gladly run another wheel, or even a third. They always opt for SA.