If both parties are armed in Florida, say Trayvon was also armed, could they have engaged in a perfectly legal lethal gunfight?
Yes.
I linked
this case before but the new link is a better summary. It was a gang shootout where (allegedly) a single shot from one side was responded to with around 24 rounds from an AK47, killing a 15 year old on the other side. Both sides claim the other opened fire first.
During a pre-trial Stand Your Ground hearing two of the men accused of manslaughter (including the one holding the gun) claimed self defence. They convinced the judge and gained complete criminal and civil immunity from prosecution for the death.
The man who drove the victim to the gunfight plead guilty to manslaughter and got three years.
That site has a
solid collection of SYG cases, including those where no charges were filed due to the law and those where the defence failed. Some other cases that jumped out on a first glance;
Domestic stabbing by an 18 year old's legal guardian after repeated confrontations and fights.
Granted immunity on appeal. Shooting of a burglar who was fleeing the scene.
No charges brought.Stabbing in a hotel room with no witnesses.
No charges brought. 15 rounds fired at his ex-wife's boyfriend. Both sides claim the other had planning to kill them.
No charges filed.Man shot in the back of the head climbing out of the water after a fight.
Jury acquitted.Another stabbing with no witnesses. 15 year old woman claims she took and used her attacker's knife when he tried to sexually assault her while she was drunk and high.
Found guilty of murder. Fuller details on this one.