You can't go wrong with either a Chuck Harris or a Take-a-Look, either on your glasses or on your helmet.
I also use the Miricycle bar-end mirrors on my 'jump on and ride, no special stuff required' bikes.
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"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey