Black Tree Design has one solitary lion-man under its Monsters category. I can't quite tell what he's holding in his hands, though.

Eureka also has a lion-man in the Chaos Egyptians category.

Does anybody make large baboons? I'm sure I've seen some recently - Obelisk miniatures maybe? 
I don't know if they're
"giant" "large" (I don't know why I read you as saying "giant", sorry about that), but Armorcast has the old Lance & Laser baboons of greater-than-animal intelligence.

