The most intense part of my trip was visiting the mountain gorillas of Rwanda. Every aspect of the experience is extreme - first, because you are on foot, crawing through a bamboo forest, getting stung by nettles and so forth. The gorillas are very close to you. Even the place is intense - Rwanda is extremely poor, and is still recovering from the 1994 genocidal massacre of over 1million people.
The rules say that you should stay 7 meters away from the gorillas, but nobody told the gorillas that. Many points I had to stop short on the trail because a gorilla was right in front of me - no more than four or five feet away. Usually the person behind me would bump into me because in the dense brush he couldn't see why I had stopped. After many occurances it happened again and I turned around to tell the guy to back off a bit - and saw only black fur. This time it was a gorilla behind me.
She gently pushed past me on the trail. I visited two different groups, on two different days. There was quite a difference in the personality of the silverbacks (the males in charge of the group). Several of them were very mellow. One of them wasn't. He charged us - just to show off, nothing serious, or anyway that is what the guide said. Of course when a 400 lb gorilla is snapping tree limbs, and running around at 30 mph while whooping it up, it is pretty impressive, whether he is serious or not.