"Frontier in Space" and "Planet of the Daleks".
Both pretty decent serials without being anything exceptional. Pertwee is typically fabulous and acerbic, which is always a joy. If there's a third Doctor serial I don't enjoy, I can't immediately recall what it might be.
"Frontier" is of course the last serial to feature the Pertwee / Manning / Delgado trio. They had great chemistry together and always managed to elevate whatever material they had to work with. It's unfortunate that the original plan for the Master ended with Delgado's death.