Ever since reading this comment by Mother Teresa around the time that I was confirmed, I have decided to only receive Holy Communion on the tongue. The priests hands are the only ones that should touch the Eucharist and sacred vessels like the chalice.
From St. Thomas Aquinas:
"Out of reverence towards this sacrament, nothing touches it, but what is consecrated; hence the corporal and the chalice are consecrated, and likewise the priest's hands, for touching this sacrament. Hence it is not lawful for anyone else to touch it except from necessity, for instance, if it were to fall upon the ground, or else in some other case of urgency" (Summa Theologica, III, Q. 82, Art. 3).
Mother Teresa's words:
When Mother Teresa was asked by Fr. George Rutler, "What do you think is the worst problem in the world today?" she replied without a moment’s hesitation: "Wherever I go in the whole world, the thing that makes me the saddest is watching people receive Communion-in-the-hand."