Downwards form Olifants, I would like to recommend Bangu, this is a bit out of the way, but mostly if you're there you have the sightings for yourself
A better route is to take the upper part of the s39, past Goedgegun, and the Piet Grobler dam is also a very nice place
Some people swear by Girivanna, I don't but it's still a nice waterhole, and definitely worth a visit. N'semani dam must be the best one in the central area, but also very busy....
My personal best is Gudzani and Gudzani-east, as well as SON-OP and Sweni, they should not be missed! Never been on the s36....but once I can go MY WAY ALONE I'll take it
I'm not an Orpen dam fan, although its a nice place. I LOVE Leeupan south of Tshokwane, and Olifantdrinkgat and Mantimahle are both worth more than one visit

N'waswitshaka (s65) is OK..provided there is water, but you do have a nice open view, a bit similar to Leeupan. Transportdam and Renosterkoppies are very productive from time to time, both are excellent dams. Lake panic....simply wonderful (but very busy lately) So is the Byamiti weir. I personally love Ampie se boorgat as well as James waterhole. Matjulu waterhole is also a must, just to see it, although there are often animals around.
Giyisenga waterhole and the s102 (rivercourse) are exceptionally beautiful and not to be missed. So is Duke's waterhole (but not in winter!) NEVER miss the s25 and the southern part of the s114, all beautiful.
As you can see, I have spend most of my time south of Letaba, and this is about to change! The dams I have left out I don't consider that good, except along the s36, where I haven't been yet. Dams around Pretorius I personally rate low.....
I'm about to go to Bateleur in December, so I'll report on that area later, and honestly can't wait!!!!!
Hope this will do
Enjoy