Are warrant officers still in use in the military?

Yes, Warrant Officers exist in several military forces. In British and Commonwealth forces (as well as some European forces, particularly those liberated by British forces during the Second World War), a Warrant Officer is the equivalent of what's known as a Senior Noncommissioned Officer (E7 and higher) in the US. In the US military, Warrant Officers are a type of technical specialist neither in the enlist or noncommissioned officer ranks.