Great Scott

The Twelfth Doctor once used the phrase "Great Scott!" upon being asked by Nardole where he'd last seen Bill Potts. (COMIC: )

The Fifth Doctor used the phrase upon encountering Ann Talbot, a woman who looked near identical to his companion, Nyssa. (TV: )

In non-valid sources
Doc Brown once shouted "Great Scott!" as the DeLorean flew behind him in a room. (WC: )

Other matters
"Great Scott" is a phrase used by Doc Brown in Back to the Future. Its usage in follows an earlier discussion regarding Back to the Future.