Baphomet

Baphomet symbol is unique to Satanism. A demonic deity and symbolic of Satan. Can be seen as jewelry.
The inverted pentacle with a goat's head is called the Sigl of Baphomet. The term may have come from two Greek words, baphe and metis, meaning "absorption of knowledge." It has been called the Black Goat, Devil's Goat as well.
It is also now being used by the masons. It can be seen on their buildings and the emblems the put on their vehicles to identify each other.
Today, the Baphomet is widely used by religious Satanists.
The Church of Satan also uses a second symbol which is an infinity sign (a figure 8 on its side).
A Roman cross is placed on top with a second, longer cross piece added beneath the top cross piece.

Inverted Pentagram

An inverted pentagram is a 5 pointed star with two points aligned upwards.
During the 20th century, Satanists inverted the upright pentacle and adopted it as their own symbol. However, the symbol is most commonly shown with the head of a goat within the pentagram as shown below.
Used in witchcraft and occult rituals to conjure up evil spirits. Satanists use it 2 points up and pagans use it one point up. Any way it is used symbolizes evil. It matters not if two points are up or one. It matters not if it has a circle around it. It still is a symbol of Satan.

Cross Of St. Peter

Peter is believed to have been crucified upside down at his own request, as he did not feel worthy to die the same way as Jesus. Therefore many Christian sects use this cross as a symbol of humility.

The Cross of St. Peter (Petrine Cross or Peter's Cross) is an inverted Latin cross traditionally used as a Christian symbol, but in recent times also used widely and incorrectly as an anti-Christ symbol, a common but popular misconception. The correct symbolism for the anti-Christ is a inverted crucifix with Jesus Christ hung inverted upon the crucifix.

It is often associated with Satanism and anti-religious attitudes, as it is considered to represent the opposite of Christianity by inverting its primary symbol, the Latin Cross.