Can a minor in Texas (17 year-old) have a concealed handgun in his or her vehicle (with parent's consent)?

Out in the country it wouldn't be as much of a problem. In any of the large cities it could be a hell of problem. While not illegal in practice a minor with a handgun in the car, if it found by police, is going to jail until your parents come get you. They will do this under the basis of the law in Texas that it is illegal for anyone under 18 to be given a firearm with out the consent of the parents. So they will have to bring you parents in to prove that they had given consent.