Which is more elastic air or water

elasticity = ability to restore to its original shape, or to resist "strain," the amount of "sheer" stress applied to an object, which tends to deform it.

Just visualizing these objects, you could speculate that putty is the most elastic, because it can undergo elastic collisions with the ground with 60+ percent efficiency. That's another way of saying that it gains the energy and momentum that you spend throwing it to the ground by about 60% or more when it jumps back up; thus it is relatively elastic

The rubber band is also pretty elastic, but it depends on the thickness. Usually rubber bands are average, and do not possess as much elasticity as a putty.

Steel is not elastic; the metallic bonds between the molecules of steel are very strong, and so it seems to resist breakage very much. But this is not the definition of elasticity: elasticity is measured by the ability of an object to reform AFTER DEFORMING; once the steel deforms, it loses its shape's integrity, and falls to pieces. Thus it cannot be considered elastic.