[This section contains technical information on photography and is intended for those who own/ plan to bring a DSLR on a safari trip.]
A telephoto lens that goes up to 400mm would be ideal, although I went on to Etosha with a Canon 70-200mm and it was fine for 80% of the time. The 20% when I needed more zoom? When we saw the pride of 11 lions and that lone cheetah.
If you're looking at the Canon camera range, I would recommend:
Canon 50D or above
100-400mm f/4.5-5.6 IS L
(I used) 70-200mm f/4.0 IS L
I found that having an f/4.0 was not an issue and would gladly stick to that if it means getting superb quality in other components of the lens (which the 70-200mm provided. Images came out crystal clear.)
If you'd like to get a second opinion on what lenses to bring on the safari, I suggest you take a look at the wildlife lens reviews done by a pro. Link is below!
Miscellaneous: [Other photography equipment to consider bringing]
1. Circular polariser - helps give the blue skies a much richer hue. Particularly useful in a place like Etosha where it's a blue sky day every single day. I don't leave the house without one!
2. Extender - if you can't get your hands on to a good telephoto lens such as the 100-400mm above, it may be helpful to get an extender that would help increase your lens' range. Canon makes a 1.4x extender. So if you put it on a 100m lens it would turn into a 140mm lens. Nifty :)
By the way, Canon also manufactures a 2x extender but more is not always better. For one, when the 2x extender is attached to some lenses, the lens' autofocus function may not fully function. Image quality typically suffers a little as well. I'd recommend the 1.4x extender.
3. Extra battery/battery grip - while on a safari, access to electricity won't come as easily as on most holidays. You really don't want to find yourself face to face with a lion at the end of the day but no battery on the camera. Trust me - I was almost in that unpleasant situation. On that note, re-charge your batteries every night at camp!
I can go on and on about photography gear. Drop me a message if you have any questions :)
Finally, if you don't intend to turn this into a major photography trip, at least make sure you bring along a pair of good binoculars with you. Otherwise, you won't be able to see a lot of the animals too clearly as they are often quite some distance away.
Toiletries and Medical Supplies: The extremely dry climate in Namibia could really be a problem for the skin. All the rough tumbling about climbing dunes, building tents, etc. don't help either. Make sure you bring some good moisturiser to keep your hands/feet from getting too dry. Cracked skin is very uncomfortable on a safari! I personally used Vaseline's Intensive Rescue Moisture Body Lotion (pictured) and found it very useful. Same thing goes for the lips - get something strong like the Vaseline Lip Therapy with Aloe Vera.