The 2 Cushing movies to explain daleks. The 8th doctor. Blink. Then rose.
Discussion
Blink is my all time favorite episode across the entire cannon.
Not my favorite, but easily the best one to explain how tone travel works in the show, introduce monsters of the week, and get people into the show.
It's just to bad the doctor is only in it for like 30 secondsš¤£