Marriage in the Catholic or Orthodox Church is a sacrament because the spouses form Church Domestic and become vehicle of grace for each other and their children, leading each other to salvation in the Church.
In a Protestant setting I don’t know what is. Logically, Baptism and Marriage should be the only two Protestant sacraments since they do not absolutely require a priest, and indeed most Protestant baptisms are valid, and so are Protestant marriages unless a Catholic is involved.
In reformed/prebyterian theology, the two sacraments are baptism and the Lord's Supper. Baptists don't have any sacraments. Marriage would be considered an ordinance. Thus while a presbyterian could have a lawful marriage not performed by an ordained man, only one lawfully ordained can administer the Lord's supper or baptize a child or adult.