The ankh (pronounced 'ahnk', symbol ☥) was the Egyptian hieroglyphic character that stood for the word ʿnḫ, which means life. Egyptian gods may carry it by the loop, or bear one in each hand crossed over their breast. Latinists interpreted the symbol as a crux ansata, "cross with a handle".
~ Wikipedia

Origins of the ankh
The original meaning of this Egyptian symbol is also not known. One suggests that it combines the male and female symbols of Osiris (the cross) and Isis (the oval) and therefore signifies the union of heaven and earth. As a hieroglyph, it likely encompassed a range of meanings depending on its associated hieroglyphs but all of these expressions centered around the concept of life or life force.

Over time, the ankh certainly came to symbolize life and immortality, the universe, power and life giving air and water. "Its keylike shape also encouraged the belief it could unlock the gates of death." The Coptic Christians used it as a symbol of life after death. The ankh has been used in ritual magic.

The ankh and the cross
"The ancient Egyptian hieroglyphic symbol of life -- the ankh, a tau cross surmounted by a loop and known as crux ansata -- was adopted and extensively used on Coptic Christian monuments."
(The New Encyclopedia Britannica, 15th edition, 1995, volume 3, page 753)

"A still more curious fact may be mentioned respecting this hieroglyphical character [the Tau], that the early Christians of Egypt adopted it [...] numerous inscriptions, headed by the Tau, are preserved to the present day on early Christian monuments."
(Wilkinson's Egyptians, by Sir J. G. Wilkinson, volume 5, page 283-284)

"The origin of the Ankh has been ascribed to a combination of the male Tau and the female oval representing
unity of the sexual organs.
it was adopted by early Egyptian Christians as their �cross�."
--SUN DISC TO CRUCIFIX; THE CROSS
A short illustrated history
Ian McNeil Cooke

-.-

The ankh and pop culture
"On the anime series Yu-Gi-Oh!, the character Shadi uses the millennium key, which is in the shape of an ankh, to unlock and enter people's minds.
~ Wikipedia

"They're being a bit more lenient on censorship these days since, previously, they were censoring stuff like crazy, but now they're letting some things slide over which is why they let Tea "grow" over Battle City and such and which is why they didn't edit out the Ankh symbol on the Monster Rebirth card Raphael uses (and Yugi uses next season) instead of changing it like they did with Monster Reborn and Monster Reincarnation, which were also Ankh symbols (the Millenium Key's shape)."
~Yu-Gi-Oh realms forum

I repeat, the ankh is not a symbol of anti-christ! And don't talk to me about Chris Angel, I don't know what he did with the ankh to make you associate it with anti-christ.. (I actually don't really care. Bleh.)

Tell me it's anti-christ one more time and I shall have to thwap you with my dead, uncooked Kunning fish!

Rar!

(The devil didn't make me do it.)