If I were doing a typical plains game hunt of 10-14 days in Namibia, and it was my first hunt my list would be as follows:
Kudu-Namibia has some monsters, and they're way cool
Gemsbuck-same reason
Springbok-the Kalahari Springbok from Namibia is the largest subspecies of Springbok
Hartmann's Mountain Zebra-can't get them anywhere else
Waterbuck-some of the Namibian ranches have some huge ones
Red Hartebeest-again, some real big ones available
Black & Blue Wildebeest-just gotta have one of each
Impala-they're just too cool not to take one
Steenbok-they make a great looking life size mount done up lying down on a rock

Eland can take up many days of your hunt
Sable are too expensive in Namibia, unless you can find a great deal on one
Blesbok-I think better ones, on average come out of RSA, although some big ones do come out of Namibia from time to time
Warthog-Namibia isn't generally known for big ones because in most places the soil is too hard and rocky
Giraffe are kind of neat, I may take one next year in Namibia