For some reason I was always a fan of the grandfather character that appeared in the season two He-Man episode "Hunt for He Man". Not only was he given a superbly fleshed-out personality, but the character design was unique. Normally, with an old character, Filmation would just reuse an existing character model to cut both time and costs. However, the character design department created a wonderfully-detailed elderly figure, somewhat hunched over. I always loved that you could really sense the frailty with the grandfather, but that he sported such a strong personality! Also, I think the color scheme of the character worked well.
(click on the image to see it at full-size)