Visited....oh man, probably most of them - definitely all the "main" denominations. I think the only ones I have not been to are the very small denominations and Oneness types. Otherwise I have been all around from Messianic, Catholic, Orthodox, Baptist (SBC, ABA), Methodist (UMC, Free), Anglican and Episcopal, Pentecostal, Non-Denom, Lutheran (ELCA, LCMS, WELS). reformed and Presbyterian (PCUSA, EPC, PCA). I have been members at several different denominations as well.
Outside of Christianity I have also been to synagogues, mosques, as well as Daoist, Shinto and Buddhist temples, but out of those I have only participated in worship at a synagogue (I am also Jewish).