Of sulfur nucleophiles, hydrogen sulfide and its salts, thiols (RSH), thiolate anions (RS), anions of thiolcarboxylic acids (RC(O)-S), and anions of dithiocarbonates (RO-C(S)-S) and dithiocarbamates (RN-C(S)-S) are used most often.
In general, sulfur is very nucleophilic because of its large size, which makes it readily polarizable, and its lone pairs of electrons are readily accessible.