Tenancy by the Entirety "TBE" only applies to married couples and is only available in a portion of the states (by statute). States that don't accept the TBE designation will either see marital assets as joint assets, separate assets, or community property.
TBE is a great marital tool to invoke creditor protection. For instance, if a rental property is titled TBE, only a creditor of BOTH spouses may take that rental property in the event of a dispute. The protection afforded to TBE property is much greater, and stronger than most other designations. Also, TBE property passes outside of probate because the property automatically passes to the surviving spouse on death.