You asked for IIT’s, anyhow IISc offers direct admission to some programs and interview for some others

IIT Bombay: Excluding Energy Science & Engg, all the specializations were given direct admission based on GATE scores

IIT Madras: For M.S. they will call ranks upto ~2500 and will select through written followed by interview. This is too good for people whose rank fall in between 1000–2000. For M.Tech they will keep on sending admission letter (5–6 rounds) based on gate scores

IIT Kanpur: Interview

IIT Delhi: Interview

IIT Kgp: Direct admission

IIT Roorkee: Online Web Counselling followed by Document verification. They will prepare their own merit list(different GATE formula for shortlisting).

IIT BHU: Shortlists 500 students for document verification and selects ~80(Incl Waiting List). Direct admission

IIT Hyd: Direct Admission for all programs

IIT Guwahati: Direct admission for M.Tech. Written+Interview for M.S or M.S+Ph.D

IIT Bhubaneswar: Written+Interview

IIT Gandhinagar: Written+Interview

IIT Mandi: Written+Interview