The Masque of Mandragora (Fourth Doctor).
An excellent story though Sarah Jane did seem to spend more time needing to be saved in this one than the past few I've watched. Saved from being sacrificed, saved from killing the Doctor, saved from the dungeons. I enjoyed the pre-renaissance Italy setting. It's too bad however that we didn't get to see the Doctor interact with Leonardo da Vinci. The potential arugments could have been interesting.
The Deadly Assassin (Fourth Doctor).
As far as I know this is the only serial from the classic era where the Doctor does not have a companion unless you count Co-ordinator Engin and Castellan Spandrell. I enjoyed this brief glimpse into Time Lord society and the small amount of history that was presented as well. The portrayal of the Master was excellent though I still prefer Roger Delgado's mix of theatrics and quiet menace.