The least differentiated type of stem cells that can become anything is Totipotent stem cells.
Totipotent stem cells have the ability to develop into any cell type in the organism, including both embryonic and extra-embryonic tissues (such as the placenta). Pluripotent stem cells can give rise to almost all cell types but not extra-embryonic tissues. Multipotent stem cells are more restricted and can differentiate into a limited range of cell types within a specific lineage.