What molecule has a central atom that is sp hybridized?
For especially carbon compounds it is very easy to identify the hybridization of the carbon. If the carbon has no double bond it is
Hence, prop-1,2-ene as a molecule with two double bonds works. (and the center carbon is the one which is sp hybridized).
You could also look at an alkyne such as propyne, which instead of two double bonds has one triple bond. Once again, the center carbon is