Having all the Doctors, including Peter Capaldi who wasn't going to take over the role of the Doctor until the next season help save Gallifrey in the 50th Anniversary episode was pretty great, even if most of them were just re-used clips from old episodes of Doctor Who.
This is mine - just because it's the only episode of TV I watched at the cinema and everyone was losing their shit {which is more unusual in the UK than cinemas elsewhere from my experience).