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

Copy-pasting your code into the module returns Run-time Error 13 (Type
mismatch).

So sorry for the slow reply, and also the wrong info.

I never noticed the Type parameter to InputBox in Excel, so my answer to
you was bogus.

My code works correctly if you set Type:=2 (text).

On the other hand, on my machine, your original code works perfectly.
You can test it by selecting the range, so maybe like this:

Option Explicit
Dim obRange1 as Range
Sub MergeLists2()
Set obRange1 = Application.InputBox(prompt:="Select first range of data
", Type:=8)
obRange1.Select
End Sub

I'm not sure why it doesn't work for you! Did you try doing it in a
completely new workbook?

Pasted into new module and added the .Select