Name: Inverted Pentagram
When used by satanic groups, the three downward points often signify rejection of the Christian Trinity.
This is a 19th century image by Eliphas Levi called the "Sabbatic Goat." The name "Baphomet," which eventually became associated with this illustration, has been around since the 13th century and at some point became linked with pagan worship.
Aleister Crowley associated the image with sex magic.
It is also depicts "the devil" in some Tarot images.
Name: Sigil of Baphomet
The Hebrew characters situated in the outer ring spell out "Leviathan."
This symbol has been used from the days of the Spanish Inquisition to the present as it is the cover art for Anton LaVey's The Satanic Bible.
(Image courtesy of Gustov89.)
Name: Cross of St. Peter
Traditionally called the Cross of St. Peter to depict the upside down crucifixion of the apostle, it was later adopted by some satanic organizations to convey a reversal of Christianity.
Name: Satanic Cross
A modification of the alchemic sign for sulfur, which represents fire and brimstone, the symbol is used in Anton LaVey's The Satanic Bible.
This six-pointed star is usually associated with Judaism, but has been used as an occult symbol going by the name "The Seal of Solomon."
Anton LaVey. The Satanic Bible. Avon Press. 1969.
Lyle Stewart. The History and Practice of Magic. Vol. II. University Books. 1979.