Dik-diks! Closely related to giraffes, dik-diks are monogamous and mate for life. If you spot one dik-dik, its mate is likely only a few feet away. They mark their territory with numerous little dung piles, so they're probably not the best pets.
We saw dik-diks in Lake Manyara National Park, and those adorable little beasts were the second-most awesome thing we saw there, behind only the 5-minute baboon fight in some trees.