George Zimmerman has figured out a way to exploit what made him famous -- GUNS.

Zimmerman did a meet-and-greet Saturday at an Orlando gun shop. People lined up for an autograph pic of Zimmerman and his dog ... actually only around 20 people lined up.

It's a page out of the OJ playbook ... get acquitted of killing someone, and then show up places and sign autographs.

One funny thing ... the pic Zimmerman signed is clearly from days past, when he weighed 50 lbs less ... and that's being generous.