The verse is as follows:
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. (KJV)
For a comparison of different translations of this verse, see Bible translations.
The phrase "John 3:16" is very short and can be written in large letters on small signs. As a result, some Christians have intentionally displayed the phrase at sporting events (such as football games) so it might be televised.
The text of the verse is also incorporated into the Divine Liturgy of St. John Chrysostom, as part of a prayer said by the celebrant. This Divine Liturgy is commonly used in the Eastern Orthodox Church and in the Byzantine rite of the Roman Catholic Church.