It is possible you are thinking of animals that lay eggs, such as the platypus and echidnas. These are considered mammals, but they are called monotremes and lay eggs instead of giving birth to live young. However, even these animals suckle their young after they hatch.
Could you please clarify your request? Perhaps you are interested in:
* Mammals that have unique or unusual ways of caring for their young: Some mammals have unusual methods of raising their young, like kangaroos that keep their young in pouches or some primates that carry their infants on their backs.
* Animals that are not mammals but share similar characteristics: There are some animals, such as birds, that exhibit parental care and feeding of their young, though they don't suckle.
* The evolution of mammalian suckling: If you're interested in how suckling evolved in mammals, there are many resources available on this topic.
Once you clarify your request, I can provide more accurate information.