A lion roar will carry for miles. Everything stops right in its tracks. It's really an amazing sound. One with a kill of a gazelle, up in a tree, sleeping and resting. You really have to look for them.
Hyenas are also fairly elusive.
Baboons, however, are right there in your face. And they're nasty, too. I remember putting together dinner the first night I was in Kenya. All of a sudden, one baboon comes and sits about 50 feet away. Just sits, looking at us.