I know of Rational Rose and we have got Rational Rose 6.
But I am looking for some other tools which are more usable, which do not complain that they are not running in
Check out Enterprise Architect. It's not expensive and does a lot of things well.
Enterprise Architect does reverse engineering and code generation for VB6
I did check out Enterprise Architect on SpareX's web site but could not find any reference stating that it handles reverse engineering or code generation for VB6.
This lists Visual Basic (as distinct from VB.Net) as supported.