The Seventh Doctor

The Seventh Doctor has a significant spot in the series.

LIST OF APPEARANCES
STORY 010 - The Two Doctors

STORY 020 - The Four Doctors

WEBCAST 3 - Mental Threat

S2S3 - The Two Doctors Prequel: A Good Question

WEBCAST 5 - Ten and Seven

SEVEN AND SIXTEEN
The Seventh and Sixteenth Doctors have often referred to themselves as best friends (STORY 020: The Four Doctors), an judging by the way they act and dress, I'd say thats safe to say.