Regarding the symbolism of the rattlesnake, Benjamin Franklin wrote:
I recollected that her eye excelled in brightness, that of any other animal, and that she has no eye-lids—She may therefore be esteemed an emblem of vigilance.—She never begins an attack, nor, when once engaged, ever surrenders: She is therefore an emblem of magnanimity and true courage.—As if anxious to prevent all pretentions of quarrelling with her, the weapons with which nature has furnished her, she conceals in the roof of her mouth, so that, to those who are unacquainted with her, she appears to be a most defenceless animal; and even when those weapons are shewn and extended for her defence, they appear weak and contemptible; but their wounds however small, are decisive and fatal:—Conscious of this, she never wounds till she has generously given notice, even to her enemy, and cautioned him against the danger of treading on her.—Was I wrong, Sir, in thinking this a strong picture of the temper and conduct of America?
Rattlesnakes just want to be left alone, happily devouring voles, mice, rats. Whatever furry varmint it can get its jaws around. To see one in the wild is both amazing and frightening, the beauty of the skin juxtaposed to the unnerving buzz of the rattle.
A variation of this flag has been used by the Free State Project, a libertarian group whose members intend to move to New Hampshire and work for the libertarian cause. Their variation features a cute, cuddly porcupine - big mistake in my estimation.
For more on the Gadsden flag, click here.