Talking about big rats - down here in South Africa we have
cane rats
Getting to be the size of a small dog, these critters make good pets and can be trained extremely easily (they do anything for food). In Mozambique they use them to find buried landmines left over from the civil war. Eaten a few in my time - quite tasty too (sorry Katy).
Weirdest African creature that I can think of in short notice is the aardvark.