If you ask me i'd have to pick from two species...the crocodile gar (Lepisosteus platostomus x Atractosteus spatula) and the alligator gar (Atractosteus spatula).
To me, the whole pattern, snout, etc. don't look much like a normal spotted or florida gar, just my opinion. How big is it? At younger ages and sizes, many gar species look alike. I really think it's somehow an alligator gar though. Hope my guess wasn't too far off.
HTH