InputBox returns a string, not an actual range, so you'll need to first
return the result to a string and then turn that into a range.

How about:

Option Explicit
Dim obRange1 As Range ' <- change
Sub MergeLists()
Dim s as string
s = Application.InputBox(prompt:="Select first range of data", _
Type:=8)
Set obRange1 = ActiveWorkbook.ActiveSheet.Range(s)
obRange1.Select ' If you want to select the specified range.
End Sub