In 1 Corinthians 1, who were Crispus and Gaius? 1 Corinthians 1:14


  14  I thank God that I baptized none of you, but Crispus and Gaius;
In the tradition of the Eastern Orthodox Church, Crispus was the ruler of the synagogue at Corinth.  He is understood to be the same Crispus that is mentioned in Acts 18:8:


  And Crispus, the chief ruler of the synagogue, believed on the Lord with all his house; and many of the Corinthians hearing believed, and
  were baptized.


He is believed to have later become the bishop of the Greek Island of Aegina and, by some accounts, is understood to have been one of the Seventy Apostles.1 

Gaius may have been the same Gaius who is mentioned in Romans 16:23:


  Gaius mine host, and of the whole church, saluteth you. Erastus the chamberlain of the city saluteth you, and Quartus a brother.


If so, he was, again according to Orthodox tradition, Bishop of Ephesus after Timothy.2



1 Life of Apostle Crispus fo the Seventy
2 Life of Apostle Gaius of the Seventy