Does the Halacha allow the use of a hamsa as a good luck charm, considering that it originated as a Muslim symbol?
Ben Ish Hai (Shana Bet Parashat Pinehas sim. 13) actually endorses the Hamsa.
A few months ago, I asked HaGaon HaRav Meir Elyiahu Shelit"a this question (question 108 on RabiMeir.com):
He admits that it is taken from the Muslims, but since a lot of big rabbis didn't protest but actually promoted it, it is simple to him that there is no Hukot HaGoyim involved.
The Wikipedia page discusses how it pre-dates Islam and seems to have pagan origins, which would be a worse problem. Good luck charms are problematic on their own, but pagan ones are definitely assur.