The Earth

In the beginning God created the heaven and the earth. (Genesis 1:1)

The Earth itself is a symbol of Christ.

All of the planets in our solar system are named after Roman gods, except for the Earth.  There is Mercury, the messenger god; Venus, the goddess of love; Mars, the god of war; Jupiter, the king of the gods; Saturn, the god of agriculture; Uranus, the god of the sky; Neptune, the god of the sea; there are even some dwarf planets named in the same manner: Pluto, god of the underworld; Ceres, goddess of agriculture; Eris, goddess of discord.  

The Earth is the only planet which holds a name that doesn't come from a mythical god. 

And it is interesting to note that Earth is the only planet which has life.  You can go to Venus, or to Mars, or to Neptune, but you will find no life there.  They are desolate, cold, and do not have the things necessary to sustain life.  Only on the planet Earth will you find life. 

And so it is with deity.  Christ is the only God that has life.  The others are dead and you will find no life in them, for they can "neither... see, nor hear, nor walk" (Revelation 9:20).  They do not answer; they do not bless; they do not live, but Christ does.  He does all of those things, because He is a true God, and He lives.  We will find life in Christ, and in no other god.

Also, the Earth is the third planet from the sun.  3 is a symbolic number. 

There are three Personages in the Godhead: God the Father, Jesus Christ, and the Holy Ghost. (Articles of Faith 1:1)

During the creation, there were no life forms until the third day when God created “grass, the herb yielding seed, and the fruit tree yielding fruit.” (Genesis 1:11-13)

And on the third day, Christ rose from the dead. (1 Corinthians 15:4)