The Robots of Death and The Christmas Invasion.

The Curse of Fenric and Under the Lake/Before the Flood

The Caves of Androzani and Vincent and the Doctor

World Enough & Time / The Doctor Falls

The War Games OR The Face of Evil OR The Invisible Enemy

The Ark in Space and Dalek

The three doctors

World enough and time/the doctor falls

For new who: Day of the Doctor and World Enough and Time/ The Doctor Falls are tied for me

For classic who: Caves of Androzani

The War Games / The Time of the Doctor or World Enough and Time

The Art of Death. Just so GOOD

TV wise, the God-tier episode that is Heaven Sent